解方程,否则无分25-2a=5+2a90-x=4(72-x)3x-2（10-x）=152x-1.8=x+2.40.72×3+4x=3.06+3x7.8x-4x=2x+3.63y+2=y-1+6y

Question

解方程,否则无分
25-2a=5+2a 90-x=4(72-x) 3x-2（10-x）=15 2x-1.8=x+2.4
0.72×3+4x=3.06+3x 7.8x-4x=2x+3.6 3y+2=y-1+6y

Answer 1

25-2a=5+2a
4a=25-5
4a=20
a=5
90-x=4(72-x)
90-x=288-4x
4x-x=288-90
3x=198
x=66
3x-2（10-x）=15
3x-20+2x=15
5x=35
x=7
2x-1.8=x+2.4
2x-x=2.4+1.8
x=4.2
0.72×3+4x=3.06+3x
2.16+4x=3.06+3x
x=3.06-2.16
x=0.9
7.8x-4x=2x+3.6
7.8x-4x-2x=3.6
1.8x=3.6
x=2
3y+2=y-1+6y
3y-7y=-1-2
-4y=-3
y=3/4