14/25×10/21 3 1/2×4 4/5÷2/25

1) 1,2x + 7 = 2x + 3

2x - 1,2x = 7 - 3

0,8x = 4

x = 5

2) 8,3 - 2,1x = 2(1,5x + 11,8)

3x + 2,1x = 8,3 - 23,6

5,1x = -15,3

x = -3

3) 9(13 - 0,8x) = 7,1x - 5 - 6,7

117 - 7,2x = 7,1x - 11,7

14,3x =  128,7
x = 9