# line spreads and mixes with next column

A line spreads and enters the next column. I am at lost to find how to correct this. the picture and code is appended, please if anyone can help.

\begin{multline*}\tag{21}
NUP_S =1- \text{probability of  successfully finishing  an  SU  service}\\
= 1 - \frac{\lambda_S(1-P^{BL}_S)(1-P^{FT}_S)}{\lambda_S}\\
= P^{BL}_S + P^{FT}_S + P^{BL}_S  P^{FT}_S\\
NUP_S= P^{BL}_S + P^{FT}_S - P^{BL}_S  P^{FT}_S\\
\end{multline*}


• Could you please post a complete compilable code, not just a snippet? – Bernard Apr 9 at 19:05
• it is simply too long, can you not use a shorter phrase or a symbol that you define rather than having probability of successfully finishing an SU service inline? – David Carlisle Apr 9 at 19:12
• also NUP should be \mathrm{NUP} see the spacing in your image, the default math italic uses wide sidebearings so adjacent letters look like a product of variables not a single multi-letter identifier – David Carlisle Apr 9 at 19:23
• @Bernard! The complete code is very long, and irrelevant I think. – Abdullah1 Apr 10 at 5:25
• @DavidCarlisle! Your suggestion is weighty... thanks – Abdullah1 Apr 10 at 5:47

You can use the linegoal package to set the parbox width so that it ends at the right side of the column (two compilations required):

\documentclass[twocolumn]{article}
\usepackage[showframe]{geometry}%
\usepackage{mathtools}
\usepackage{linegoal}
\usepackage{lipsum}

\begin{document}

\begin{equation*}\tag{21}
\begin{aligned}
NUP_S & =1- \rlap{\parbox[t]{\linegoal}{probability of successfully finishing an SU service}}\\
& = 1 - \frac{\lambda_S(1-P^{BL}_S)(1-P^{FT}_S)}{\lambda_S}\\
& = P^{BL}_S + P^{FT}_S + P^{BL}_S P^{FT}_S\\
NUP_S & = P^{BL}_S + P^{FT}_S - P^{BL}_S P^{FT}_S\\
\end{aligned}
\end{equation*}

\lipsum

\end{document}


• if i have repeat three such equation in document, all three appear differently (position of equation number, formatting of text) ... why? – Zarko Apr 9 at 20:07
• Exactly the same three equations? Note my usage of \rlap for the text in the 1st line: without it, the equation number would be under the last line. – Bernard Apr 9 at 20:15
• in my test numbers appears at all equation at the vertical middle (i use the same equation as you provide in answer), but the text at each second equation is broken onto 12 lines. – Zarko Apr 9 at 21:56
• Could you open a question and post the exact code that produces this problem? – Bernard Apr 9 at 21:58
• – Zarko Apr 9 at 22:41