3X-3×3= 18

3X-9= 18

3X= 18+9

3X=27

x = 27 \3

X=9

2, X÷2= two thirds.

X÷2×2= two thirds× 2

X= four thirds

X= one and a third

3、 12(X+3.7)= 144

12X+ 12×3.7 = 144

12X+44.4= 144

12X= 144-44.4

12X=99.6

X=99.6÷ 12

X=8.3

4、5X-3× 1 1=42

5X-33=42

5X=42+33

5X=75

X= 15