solve in simultaneous method
a+2b=13
2a-3b=5
a+2b=13 ... multiplying by 2 ... 2 a + 4 b = 26
2a-3b=5
subtracting equations (to eliminate a) ... 7 b = 21
solve for b , then substitute back to find a
a+2b=13
2a-3b=5
2a-3b=5
subtracting equations (to eliminate a) ... 7 b = 21
solve for b , then substitute back to find a