maths(right,very esay

题目

maths(right,very esay
①（1-y)/2=2-[(2y-1)/3]
②21%x-5%=5%x+0.11
③(2y-1)/3-(10y+1)/6=(2y+1)/4-1
④1/3[3y-(10-7y)/2)]-1/2[2y-9(2y+2)/3）]=y/2-1
⑤(0.4y+0.9)/0.5-(0.03+0.02y)/0.03=（y-5）/2

答案

①（1-y)/2=2-[(2y-1)/3]
两边乘6
3-3y=12-4y+2
4y-3y=12+2-3
y=11
②21%x-5%=5%x+0.11
0.21x-0.05=0.05x+0.11
0.21x-0.05=0.11+0.05
0.16x=0.16
x=1
③(2y-1)/3-(10y+1)/6=(2y+1)/4-1
两边乘12
4y-2-20y-2=6y+3-12
6y+20y-4y=-2-2-3+12
22y=5
y=5/22
④1/3[3y-(10-7y)/2)]-1/2[2y-9(2y+2)/3）]=y/2-1
两边乘6
6y-10+7y-6y+18y+18=3y-6
25y+8=3y-6
22y=-14
y=-7/11
⑤(0.4y+0.9)/0.5-(0.03+0.02y)/0.03=（y-5）/2
两边乘3
2.4y+5.4-3-2y=1.5y-7.5
1.1y=9.9
y=9