Three times andy's age is eleven more than twice belinda's age. the sum of their ages is two less than twice belinda's age. how old is each person

A=andy's age
b=belinda's age

3a=11+2b

a+b=-2+2b

wowie

a+b=-2+2b
minus b from both sides
a=b-2

subsitute b-2 for a

3a=11+2b
3(b-2)=11+2b
3b-6=11+2b
minus 2b from both sides
b-6=11
add 6 to both sides
b=17

subsitute

a=b-2
a=17-2
a=15
andy is 15
belinda is 17