1) 5x - 7 = -21 - 2x
=> 5x + 2x = -21 + 7
=> 7x = -14
=> x = -2
2) x + 15 = 20 - 4x
=> x + 4x = 20 - 15
=> 5x = 5
=> x = 1
3) 17 - x = 7 - 6x
=> 17 - 7 = -6x + x
=> 10 = -5x
=> x = -2
1) 5x - 7 = -21 - 2x
-2x - 5x = -7 + 21
-7x = 14
=> x = -2
2) x+ 15 = 20 - 4x
-4x - x = 15- 20
-5x = -5
x = 1
3) 17 - x = 7 - 6x
-6x + x = 17 - 7
-5x = 10
x = -2