please mohon dijawab

3a + 4b = 5 dikali 2 = 6a + 8b = 10
5a + 6b = 7

6a + 8b = 10
5a + 6b = 7
__________-
a + 2b = 3
a = 3 - 2b

disubtitusi
5(3 - 2b) + 6b = 7
15 - 10b + 6b = 7
-4b = -8
b = 2
a = 3 - 2(2)
=3 - 4
= -1
{2,-1}