Nilai (2x + 5y) yang memenuhi sistem persamaan {3x - 4y =15 dan 5x + 4y = -7} adalah ...

3x - 4y = 15
5x + 4y = -7
_________+
8x = 8
x = 1

3x - 4y = 15
3(1) - 4y = 15
3 - 4y = 15
-4y = 12
y = -3

2x + 5y = 2(1) + 5(-3) = 2 - 15 = -13

3x-4y=15
5x+4y=-7
-------------- +
8x = 8
x = 1

5 (1) + 4y = -7
4y = -7 - 5
4y = -12
y = -3

2x+5y = 2 (1) + 5 (-3)= 2 - 15 = -13

semoga membantu :)