Answer
$(5,2) $ is a solution of the system.
Work Step by Step
A solution of a system of two equations in two variables is an ordered pair of numbers that makes both equations true.
Substituting $a=5, b=2$ into each equation,
$a+b=7$
$5+2\stackrel{?}{=}7$
$7=7,\qquad $...the first equation is true for $(5,2)$
$2a-8=b$
$2(5)-8\stackrel{?}{=}2$
$10-8=2\qquad $...the second equation is true for $(5,2)$
$(5,2) $ is a solution of the system.