5、
(5a+3b)÷8=0.1375
5a+3b=1.1.(1)
(3a+5b)÷8=0.1625
3a+5b=1.3.(2)
(a+2b+5c)÷8=0.3125
a+2b+5c=2.5.(3)
(1)*5-(2)*3:25a-9a=5.5-3.9
16a=1.6
a=0.1=10%
代入(1):5*0.1+3b=1.1
3b=0.6
b=0.2=20%
代入(3):3*0.1+2*0.2+5c=2.5
5c=1.8
c=0.36=36%
5、
(5a+3b)÷8=0.1375
5a+3b=1.1.(1)
(3a+5b)÷8=0.1625
3a+5b=1.3.(2)
(a+2b+5c)÷8=0.3125
a+2b+5c=2.5.(3)
(1)*5-(2)*3:25a-9a=5.5-3.9
16a=1.6
a=0.1=10%
代入(1):5*0.1+3b=1.1
3b=0.6
b=0.2=20%
代入(3):3*0.1+2*0.2+5c=2.5
5c=1.8
c=0.36=36%