Answer:
The correct answer would be 
Step-by-step explanation:
given
we want to solve for a
How?
We can do this by using basic algebra ( isolating the variable (a ))
Step 1 subtract
from each side

now we have 
step 2 take the square root of each side

we're left with
Hence your answer is A
Hello!
To factor you find the biggest number they can be divided by
The biggest number that all the number can be divided by is 10
You put that outside parenthesis
10()
Divide the expression by 10
3 + x - 4y
Put the two together
10(3 + x + 4y)
Hope this helps!