20,000 would be the answer
12a=x
4a+6b=10
2a+3b=5
2a-4b=12
a-2b=6
2a+3b+1=a-2b
a+5b+1=0
a=-1-5b
2(-1-5b)+3b=5
-2-10b+3b=5
-2-7b=5
-7b=7
7b=-7
b=-1
-1-5*-1=a
-1+5=a
4=a
4*12=48
12a=48
Hope this helps :)
Took 3 of us in grade 10 but johns present age is 77.5 and his sister is 72.5
64% of 75 = 64/100 x 75 = 48 <==== answer
