Use Slack Variables to Rewrite This Problem So That All $\mathrm { MAX } : \quad 2 \mathbf { X } _ { 1 } + 7 \mathbf { X } _ { \mathbf { 2 } }$

Use slack variables to rewrite this problem so that all its constraints are equality constraints.
$\mathrm { MAX } : \quad 2 \mathbf { X } _ { 1 } + 7 \mathbf { X } _ { \mathbf { 2 } }$
Subject to:
$$\begin{array} { l } \mathbf { 5 } \mathbf { X } _ { 1 } + \mathbf { 9 } \mathbf { X } _ { \mathbf { 2 } } \leq 90 \\\mathbf { 9 } \mathbf { X } _ { 1 } + \mathbf { 8 } \mathbf { X } _ { \mathbf { 2 } } \leq 144 \\\mathbf { X } _ { \mathbf { 2 } } \leq \mathbf { 8 } \\\mathbf { X } _ { 1 } \mathbf { X } _ { \mathbf { 2 } } \geq 0\end{array}$$