Answer:-10
1. Make equation:
X + 17 + X + 20 = 17
2. Short the equation:
2x + 17 + 20 = 17
3. Make numbers to the left side, without forgetting to change sign:
2x = 17-17-20
2x = -20 |:2
x = -10
Proof: (Solving equation)
(-10)+17+(-10)+20 =
(-10)+17-10+20 =
7-10+20 = -3+20 = 17
So the answer is -10