9)
a+b=631 => a=631-b
a:b=3 r 7 => a=3b+7
inlocuim in relatie:
3b+7+b=631
4b+7=631
4b=631-7
4b=624
b=624:4
b=156
a=156*3+7
a=468+7
a=475
verificare:
475+156=631
475:156=3 r 7
10)
f+b=30 elevi => f=30-b
b-2=f:3 => f=(b+2)*3 => f=3b+6
inlocuim in reletie:
3b+6+b=30
4b=30+6
4b=36
b=36:4
b=9
a=(9-2)*3
a=7*3
a=21
21+9=30
21:3=9-2
7=7
