How do you write out an equation for a word problem?

Question

I need to define the variable, write an equation, and solve for the following problem. I can determine the answer, but I don't know how to write out the problem:

Cassie is 9 years older than her brother. Three years ago, Cassie was 4 times as old as her brother. How old is each person now?

The answer is Cassie is 15 and the brother is 6. But how do I define the variable and write out the equation?

Let b = brothers age now
B + 9 = Cassie’s age now

That is about as far as I can get with this problem.

Answer 1

You're correct, B + 9 = C is one equation.

The other equation is:

Three years ago, Cassie was C - 3 and her brother was B - 3, and according to the second sentence:

4(B - 3) = C - 3
4B - 12 = C - 3

So take the first equation and plug it in for C:

4B - 12 = (B + 9) - 3
4B - 12 = B + 6
3B = 18
B = 6

Then, C = B + 9 = 15.

Answer 2

Let b = brothers age now
b + 9 = Cassie’s age now

b-3 = brothers age 3 years ago
b+9-3 = Cassie’s age 3 years ago

But we also know that Cassie’s age 3 years ago = 4 times as old as her brother = 4(b-3)

so, b+9-3 = 4(b-3)
b+6 = 4b -12
3b = 18
b=6

So cassie = 6+9 = 15

Answer 3

Create a variable for each unknown in the text.
B = age of brother now
C = age of Cassie now

B + 9 = C
C-3 = 4 * (B-3)

Answer 4

C=B+9
(C-3)=4(B-3)
C-B=9
C-4B=-12+3=-9
subtracting
3B=18
B=6
substituting in C-B=9
C=15

Answer 5

a million. (2)(8x-5) 2. (2)(5y-10) 3. 12x-30 the following they're, the first 2 are only doubling, so that you're taking a the vast form (or this situation the equation) and multiply by two. third you're taking the salary, and multiply it by the fashion of hours you paintings. and then take that effect and subtract 30. wish I helped.