Tom is 4 more than twice andrew's age. sara is 8 less than 5 times andrew's age. if tom and sara are twins, how old is andrew?

T=2A+4 
S=5A-8
If Tom and Sara are 10 years old,
10=2A+4
6=2A
3=A
Not sure though

Andrew= 4 years old
Sara= 12 years old
Tom= 12 years old
Basically, I did guess and check. First I started with Andrew 10 years old. I kept going down until I reached Andrew as 5 years old. I went 1 number down to 4 and that was perfect because that way Tom and Sara had the same age.