Question 555082
I do not know what the lesson said, but that system is begging you to solve equation {{{5x = y + 6}}} for {{{y}}} so you get "y = .." and then substitute the expression found for {{{y}}} into equation {{{2x - 3y = 4}}}
In substitution, the first step is to solve for x or for y in one of the equations. The espression you find is simpler if you solve for a variable whose coefficient is 1 or -1. Otherwise you may have to work with fractions, and mistakes are more likely.