解
(1)x-0.75x=12
0.25x=12
1/4x=12
x=12×4
x=48
(2)2.8x+x=7.6
3.8x=7.6
x=7.6÷3.8
x=2
(3)2.36x+2.64x=18
5x=18
x=18÷5
x=3.6
(4)3.5x-1.5x=10.8
2x=10.8
x=10,8÷2
x=5.4