Five years ago, tim’s mom was three times tim’s age today. now their combined ages are 45. how old is tim’s mom today?

X   -    age of Tim 5 years ago 
x+5 -age of Tim now
(x+5)*3- Tim's mom 5 years ago
(x+5)*3+5 - Tim's mom now
x+5 +(x+5)*3+5 Tim and his mom together now
x+5 +(x+5)*3+5=45
x+5+3x+15+5=45
4x+25=45
4x=20
x=5

(x+5)*3+5 - Tim's mom now
(5+5)*3+5= 10*3+5=35   Tim's mom now

Letter a i would say