x=3 si y+z=10
a) 7x+7y+7z=7x+7(y+z)=7*3+7*10=21+70=91
b) 17x+17y+17z-10=17x+17(y+z)-10=17*3+17*10-10=51+170-10=211
c) 5x+10y+10z=5x+10(y+z)=5*3+10*10=15+100=115
d) 100x-(9y+9z)= 100x-9(y+z)=100*3-9*10=300-90=210
2.
a) 2348:15=156 si rest 8
b) 125 673:32=3927 si rest 9
c) 987:123=8 si rest 3
3) x=100×99+98=9900+98=9998