you can solve this algebratically (pretty sure i mispelled that) or by graphing, I assume your teacher wants you to do it by graphing but i'll do it both way.
Graph: y = 4x - 8 y=3x + 5 and see where they intersect, (using a graphing calculator) they intersect at x= 13 y =44 (13, 44)
Algebra:
4b - 8 = 3b + 5 subtract 3b from both sides
b - 8 = 8 now add 5 to both sides
b= 13 (b is the equivilent or the same as x)
now take b and substitute it into the equation
4(13) - 8 = 3(13)+5
44=44