Răspuns:
a. a/3=7/10
10a=3×7=>a=21:10=>a=2,1
100a=100×2,1=210
b. 2/7=a/15
2×15=7a=>a=30:7=>a=4,28
28a=28×4,28=119,84
c.8x=3×36=>x=108:8=>x=13,5
16x=16×13,5=>x=216
d.x²=4×5=>x²=20
5x²=5×20=100
e. ab=5×0,7=>ab=3,5
10ab=10×3,5=35
f. ab=9×4=>ab=36
(36+8)/40=1,1
g. ab=7×4=>ab=28
3×28+2020=2104
h. xy=3×0,9=2,7
5×2,7+6,5=20
