4.
a/3=7/b
ab=3×7=21
ab-1=21-1=20
3a/5=1/b
3ab=5
3ab+5=5+5=10
5.
a.
30/100×150=3×15=45
b.
27/100×a=216
a=216×100/27(faci calculele)
c.
p/100×180=45
p=100×45/180 (calculele)
6.nu stiu
7.
4muncitori.....2muncitori
6zile................xzile
4,2invers proportionale 6,x
4×6=2x
x=12zile
