Answer:
3x + 9 = 21
Step-by-step explanation:
Let Henry's age be x
Mary's age = 9 + 3x
21 = 9 + 3x
Can also be written as 3x + 9 = 21
Answer:
they are just multiplying thr numbers on top for exsample 42÷6=7
Step-by-step explanation:
you should see what numbers dose the bottom numbers have in common and multiply by 15.
Answer:
the first one
the first one Step-by-step explanation:
the first one Step-by-step explanation:from the formula Un =ar^n-1
where a is 2
where a is 2 r = 20/2=10
where a is 2 r = 20/2=10 so Un= 10×2^n-1
that's all.....have fun
Hi,
Here are the equations:

He started with 10 comic books.
Hope this helps.
r3t40