book Maths Puzzle Numerical Ability

I NEED TO SET UP AN EQUATION FOR THIS WORD PROBLEM:
THE DIFFERENCE OF TWO NUMBERS IS 7, AND THEIR SUM IS 49. FIND THE TWO NUMBERS.

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book Other Question

This has to do with powers, roots, and radicals. I have a few that i have no clue how to do, they are as follows:
1. f(x)=square root of x+1
2. f(x)=little 3 square root of 5x This question is actually about elimination because there werent any catorgories for elimination. My question is:
3x+y=1
5x-y=1

Thanks for the help!