algebraic word problems?

Question

Mona's age is 4 times Billy's age. The sum of their ages is 15. Find the age of each.

PS--there are supposed to be two equations
EX1:
x+y=2y
4y-2x=0

Answer 1

sum of their age equals 15
mona is 12, billy is 3
12= 3 times 4
12+3=15

Answer 2

Mona is 4 times Billy, therefore m = 4b.

If the age of both total is 15, than "m + b = 15". Replace m with 4b because they are the same (right?). "4b + b = 15" is the same as:

5b = 15

Divide, you get 3. Billy is 3, 4 times that makes Mona 12.

Answer 3

You can solve this with linear combinations.

With the information you can get two equations to find the solution:
4x=y
x+y=15

x is Billy. y is Mona.

What you want to do is add/sub. variables to cancel one out and get the value of the other one. So, first you would move the y in the second equation to the right side of the equal sign, making it negative on the other side.

4x=y
x=-y+15

So it will be

4x = y
+ x = -y + 15
---------------------

Add the 4x and x to get 5x and y and -y cancels out

4x = y
+ x = -y + 15
---------------------
5x = 15

Divide each side by 5 to get x=3. Billy is 3.

Take one equation and substitute x with 3. It will work for both of them:

4(3)=y
y=12

(3) + y= 15
3 + y = 15
Subtract 3 from both sides to isolate x.

y=12

Mona is 12.

So Mona-12, Billy-3

To check to make sure it is the right answer, substitute in both variables in the equations:

4(3)=12
True.

3+12=15
True.

Answer 4

Let M be Mona's age and B be Billy's. The first equation:

M = 4B

Mona's age is four times Billy's age.

The other is

M + B = 15

The sum of their ages is 15.

The solution is what the other two posted.

Answer 5

Mona's age = x
Billy's age = y

x=4y
x+y=15

so substitute for x in the second equation and get
4y+y=15

simplified to 5y=15
so y=3
Billy is 3 years old

Now find Mona's age
x=4y so
x=4*3
x=12
Mona is 12 years old

Answer 6

Let x = Billy's age, then Mona's age is 4x
4x + x =15
5x =15
x = 3 (Billy)
4x = 12 (Mona)
___________________
Sum of ages= 15

Answer 7

(m+4b=15) m being Mona (12), b being Billy(3), 15 being the answer

Answer 8

let x = monas age
let y = billys age

4y+x=0
x+y=15

use substitution////
y=15-x

4(15-x)+x=15
60-4x+x=15
45=3x
15=x

Answer 9

m=4b

b+m=15

b+4b=15

5b=15

b=3

m=4(3)

m=12

Mona is 12, Billy is 3

Answer 10

4b=m
m+b=15
then u use the substitution method.
(4b)+b=15
5b=15
--- ---
5 5

b=3
billys age is 3
4(3)=m
12=m
Molly is 12