Question

1) -7+x=13; 2) x+(-9)=-4

Answer 1

1.)-7+x=13
x=13+7
x=20
Проверка
-7+20=13
ИЗИ
2)x+(-9)=-4
x=9+4
x=13
ПРОВЕРКА 
13+(-9)=-4
ИЗИ