x:3=75 75:x=3 x+23=28 65-x=50 решить уравнения

1) x : 3 = 75
x = 75*3
x = 225

2) 75 : x = 3
x = 75/3
x = 25

3) x + 23 = 28
x = 28 - 23
x = 5

4) 65 - x = 50
-x = 50 - 65
-x = -15
x = 15