Algebra/Geometry help please?

Point S is between R and T on RT. Use the give information to write on equation in terms on x. Solve the equation. Then find RS and ST.
Problem 1:
RS=2x+10
ST=x-4
RT=21
Please provide a detailed explanation of how you solved the problem. I just need help understanding it. I will try to do the next problem by myself. However, it would help if you did the next problem so that I may check my work afterwards. Thank you.
Problem 2:
RS=3x-16
ST=4x-8
RT=60

shibashis2013-09-03T16:03:36Z

Assuming RT is a straight line RT = RS + ST

or, 21 = (2x+10) + (x-4) = 3x + 6
or, 3x = 15
or, x = 5

RS = 2x+10 = 2*5 + 10 = 20
ST = x-4 = 5-4 = 1