Simplify: 20x / 5

Simplify:5×2-50                  

Simplify:

13-8+11÷4×9

Simplify: (5xy) (-4)

Simplify:2+3-1                       

Simplify:(6-5)+(10-9)

Simplify: -x+7x+10y-8y

Simplify:10-5+(-15)               

Simplify:2×3+6÷3                   

Simplify: 3x (2)