Question

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?
4, 1
-19, 40
20, 1
30, 9
-8, -29

Answer 1

Any ideas?

Answer 2

you can write a system of equations,
\(\large\color{black}{ a-b=21 }\)
\(\large\color{black}{ 5a-2b=18 }\)

Answer 3

I was thinking to put absolute values, but though it would in fact be wrong to do that.

Answer 4

can you solve the system?

Answer 5

Any questions @zxcvbnm08765 ?

Answer 6

no @SolomonZelman

Answer 7

lets start from multiplying the first equation of the system times -2, or times 5 (which ever way you like) and adding the equations together.

Answer 8

I mean or times -5. not times 5.

Answer 9

is a=-21 and b = -24/5

Answer 10

you solved the system in your head?

Answer 11

yea