24-0.5X= 12.8

0.5X=24- 12.8

X=22.4

(24.5-X)×2- 13=20

49-2X- 13=20

2X=36-20

X=8

5X-X+ 1.8=3.6

4X=3.6- 1.8

X= 1.8÷4

X=0.45

(X+2. 1)÷3= 10.5

(X+2. 1)÷3×3= 10.5×3

X+2. 1=3 1.5

X=3 1.5-2. 1

X=29.4

3.5×X= 105

X= 105÷3.5

X=30

13.06-X=8.07

X= 13.06-8.07

X=4.99

0.2(X-3.5)= 1

0.2X-0.7= 1

0.2X= 1+0.7

X=8.5

12X-3.5X+85

This problem is not an equation.

1.2X-X=35

0.2X=35

X=35÷0.2

X= 175

3-3 times =0.3

3X=3-0.3

3X=2.7

x = 2.7 \3

X=0.9

3.5×6-0.2X= 1 1.4

2 1-0.2X= 1 1.4

0.2X=2 1- 1 1.4

0.2X=9.6

X=48

3.5×(6-0.2X)= 17.5

2 1-0.2X= 17.5

0.2X=2 1- 17.5

0.2X=3.5

X=3.5÷0.2

X= 17.5