Answer:
common denominator is 40
Step-by-step explanation:8x5=40
10x4= 40
3x5=15
3x4=12
15/40 and 12/40
A
rational number is any number that can be written as the
ratio between two other numbers i.e. in the form

Part A:
An easy choice that makes sense is 7.8, right in the middle. To prove that it's rational we need to write it as a ratio. In this case we have

Part B:
We need a number that can't be written as a ratio (because it neither terminates nor repeats). Some common ones are

,

,

and

so it makes sense to try and use those to build our number. In this case

works nicely.
y = total cost used.
x = additional minutes
y = $49.95 + $0.15x
$61.20 = $49.95 + $0.15x. Subtract the $49.95 from each side.
$11.25 = $0.15x. Divide each side by $0.15
75 = x.
Michael used 75 additional minutes.