Question

Aflați cifra a , știind ca: aa+a= 72

Answer 1

aa+a=72
10a+a+a=72
12a=72
a=6

66+6=72

Answer 2

$aa+a=72 \\ 10a+a+a=72 \\ 11a+a=72 \\ 12a=72 \\ 12a-72=0 \\ 12*(a-6)=0 \\ a-6=\frac{0}{12} \\ a-6=0 \\ a=0+6 \\ a=6$