Answer:
i think 4
Step-by-step explanation:

A. 12*x + 2*y = 90
6*x + 2*y = 60
To write system of equation you just need to sum all solo and ensemble acts and make it equal to how much they will last for.
B. Here we can multiply second equation with negative 1 and add it to first equation.
6x = 30
x = 5
now we replace x in any of 2 equations to get y.
30+2y = 60
2y = 30
y=15
Solo acts are 5 minutes long and ensemble acts are 15 minutes long
Answer:
21 yrs old
Step-by-step explanation:
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
60, 60 and 60 degrees
There are two criteria: the angles have to all be equal and they have to add up to 180 degrees. This answer satisfies both criteria.