1. m+n=17 ; m=17-n
n+p=15 ; p=15-n
p+m=18 ;
15-n+17-n=18
15+17-18=n+n
2n=32-18
2n=14
n=14:2
n=7
m+n=17
m+7=17
m=17-7
m=10
n+p=15
7+p=15
p=15-7
p=8
2. 42+7÷7-(42+7)÷7<(1+2×3×8)÷7
42+1-49:7<(1+6 × 8) :7
43-7<(1+48):7
36<49:7
36<7 nu este adevarat
3. (9+6):[(9×6)-49]=
=15:[54-49]=
=15:5=
=3