Question

Stiind ca ax+ay-8=100 si x+y=12, calculati a-(x+y-7)

Answer 1

ax+ay=108
a(x+y)=108 dar x+y=12
a*12=108
a=9

a-(x+y-7)=9-(12-7)=4

Answer 2

$ax+ay-8=100 \\ x+y=12 \\ a-(x+y-7)=? \\ ax+ay-8=100 \\ a(x+y)-8=100 \\ 12a-8=100 \\ 12a=100+8 \\ 12a=108 \\ a=108:12 \\ a=9 \\ \boxed{a-(x+y-7)=9-(12-7)=9-5=4}$