(1)5x- 1 4 ×8=10 (2)12x+1.5=5.1 (3)5.5x-1.3x=12.6 (4)5(x-2.8)=140.
(1)5x-
5x-2+2=10+2, 5x÷5=12÷5, x=2.4; (2)12x+1.5=5.1, 12x+1.5-1.5=5.1-1.5, 12x÷12=3.6÷12, x=0.3; (3)5.5x-1.3x=12.6, 4.2x=12.6, 4.2x÷4.2=12.6÷4.2, x=3; (4)5(x-2.8)=140, 5(x-2.8)÷5=140÷5, x-2.8=28, x-2.8+2.8=28+2.8, x=30.8. |