Answer:
45
Step-by-step explanation:
9 into 6 is 54 and 9 into 5 is 45 rest u can understand
B just trust me I am right !
Here is the equation:

⇒

You need to get "x" by itself so minus 3 from each side

⇒

⇒

Divide 8 by 2

÷

x=4
So each 4 is equivalent to 4
Lets check:

⇒

⇒

So that means that Marcus practiced the piano for 4 hours and Donnel practiced for 7