Explicație pas cu pas:
a) D15=1,3,5,15
b)6 multiplii al nr 12=12,24,48,60,72,84
c)suma nr prime de o cifra=2+3+5+7=17
d)x+y=64/ × -2
x+2y=85
=>-2x-2y=-128
+ = -x/= -43/ -1
=> x=43=> y=64-43=21
