First Equation,
10x + 15y = 20
Second Equation,
- 9x - 15y = - 21
First Equation + Second Equation,
10x + 15y -9x -15y = 20 - 21
x = -1
Substituting value of x in First Equation,
10(-1) + 15y = 20
-10 + 15y = 20
15y = 30
y = 2
Hence, the solution is (-1, 2)