Answer:
36
Step-by-step explanation:
Just multiply 3 by 12 [1 year in 12 months] to get a total of 36 mice.
21 yrs old
m= michael age
b=Brandon age
m=b+12
m-17=4(b-17)= 4b-68 --»»m = 4b -51
//put b+12 instead m// b+12=4b-51
3b=63 --»»b=21
Brandon age is 21
Michael age is 33