The difference of two numbers, a and b, is 21. The difference of 5 times a and two times b is 18. What are the values of a and b?

Question

debbieg · Answer

Set up 2 equations. 

In one, use the fact that the difference a - b is 21
In the other, use the fact that the difference between 5a and 2b is 18 (how would you write that?).

anonymous · Answer

the diference of a and be can be written as $a-b$

We know 2 things:
 
1. $a-b=21$
2. $5a-2b=18$

From those, you can solve for either a or b and then plug it back into the equation for b

debbieg · Answer

Solve the first for either a or b (as is probably easier, but you can do either) then substitute it back into the 2nd equation. You'll solve for one variable, the sub back in to solve for the other.

anonymous · Answer

Exactly. teamwork Debbie :-p

@DebbieG

anonymous · Answer

A. 4, 1 B. -19, 40 C. 20, 1 D. 30, 9 E. -8, -29