Work is provided in the image attached.
Answer:

Step-by-step explanation:
we know that
-----> by central angle
see the attached figure to better understand the problem
we have


substitute


Well, you already have the decay model, so just plug that in
<span>2x+3y=7
x-y=1
</span>2x+3y=7
x=1+y
2*(1+y)+3y=7
x=1+y
2+2y+3y=7
x=1+y
5y=5 |(:5)
x=1+y
y=1
x=2
CHECK:
2x+3y=7
x-y=1
2*2 + 3*1 = 7
x-y = 1
2-1 = 1
I think it would be 2 and a half hours/ 2 hours and 30 minutes.