Question 245730
let a= first person
b=second person
c=third person
a+b+c=80
b=2a
a=b/2
c=b-5
three variables and three equations
substitute
b/2+b+b-5=80
combine
2.5b=85

multiply both sides by 2
5b=170
divide both sides by 5
b=34
a=17=b/2
c=29=b-5
34+17+29=80