word problems

Question

Erica earned a total of $50,450 last year from her two jobs. The amount she earned from her job at the store was $1,250 more than three times the amount she earned from her job at the college. How much did she earn from her job at the college?

Answer 1

s + c = 50,450

s = 3c + 1250

 

I'll show you two ways to do this.

 

First, simple substitution. Since s = 3c + 1250, the two sides are interchangeable. We'll substitute 3c + 1250 for s in the first equation.

 

3c + 1250 + c = 50,450

4c = 49,200

c = $12,300

 

Now, we have a value for c, which we can put into either equation to solve for s.

 

s = 3(12,300) + 1250

s = 36,900 + 1250

s = $38,150

 

Another way is to solve the first equation for s, or get it by itself.

 

s = 50,450 - c

 

Now, s = 50,450 - c and 3c + 1250, so they equal each other!

 

50,450 - c = 3c + 1250

-4c = -49,200

c = $12,300

 

Solve for s in the same manner as before.