Answer:
13x for A, 7f for B
Step-by-step explanation:
8x+5x=13x (Because 8+5=13)
9f+10f=19f
Subtract 12f and you get 7f
Answer for A is,
[tex]13x[/tex]
The answer for B is,
[tex]7f[/tex]
hope it helps.
