It is convenient to simplify the expression first:
[tex] 5x-2y+7x-y = 12x-3y [/tex]
Now let's plug the values: we substitute x = 7 and y = -2:
[tex] 12x-3y = 12\cdot 7 - 3 \cdot (-2) = 84 + 6 = 90[/tex]
