The difference between 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?
Here are the equations:
a-b=21
5a-2b=18
Multiply the first equation by 5
5a-5b=105
5a-2b=18 --subtract--
-3b=87
b=-29
So, b=-29 and a=50