1) a+b=28 ==>b=28-a
a×0,75=b+7
a×0,75=28-a+7
75a/100=35-a /×100
75a=3500-100a
75a+100a =3500
175a=3500
a =3500/175
a=20
b=28-20=8
verificare:
20×0,75=8+7
15=15
Raspuns:
a=20
b=8
2) a-0,5=a×0,5
a-5/10=5a/10 |×10
10a-5=5a
10a-5a=5
5a=5
a=1 (numarul)
verificare:
1-0,5=1×0,5
0,5=0,5