Question

1. -15 + ____ = 20
2. _____ + 18 = –17
3. 19 + ___ + – 7 = – 38
4. – 28 + _____– – 31 = 15

Answer 1

¡Hola!

$1. \: - 15 + x = 20 \\ \\ x = 20 + 15 \\ \\ \boxed{x = 35} \\ \\ - 15 + \boxed{ 35} = 20$

$2. \: x + 18 = - 17 \\ \\ x = - 17 - 18 \\ \\ \boxed{x = - 35} \\ \\ - \boxed{35} + 18 = - 17$

$3. \: 19 + x + ( - 7) = - 38 \\ \\ 19 + x -7 = - 38 \\ \\ x = - 38 - 19 + 7 \\ \\ x = 57 - 7 \\ \\ \boxed{x = 50} \\ \\ 19 + \boxed{ 50} + ( - 7) = - 38$

$4. \: - 28 + x - 31 = 15 \\ \\ x = 15 + 31 + 28 \\ \\ \boxed{x = 74} \\ \\ - 28 + \boxed{ 74} - 31 = 15$

Espero que sirva y saludos.