Answer:
Below in bold.
Step-by-step explanation:
Ab = ut
Divide both sides by b
A = ut/b.
The other 2 are solved in a similar way:
Kc = 9a
c = 9a/K
Bd = Ca
d = Ca/B.
For this case we have the following system of equations:

We solve by the substitution method:
We substitute the first equation in the second equation:

We apply distributive property considering that 

We subtract 69 from both sides of the equation:

We divide by 8 on both sides of the equation:

We look for the value of the variable y:

Thus, the solution of the system is 
Answer:

Brenda earns $1,700 per month after taxes. She is working on her budget and has the first three categories finished.Housing $612
Food $238
Transportation $370
What is the problem with this budget?
The answer is => She has allotted more than 36% of her income for housing
1. 84 = 1 x 84
2. 84 = 2 x 42
3. 84 = 3 x 28
4. 84 = 4 x 21
5. 84 = 6 x 14
6. 85 = 7 x 12
Hope this helps!