Question

find the solution of each equation if the replacement sets are x:{1,3,5,7,9} and y:{2,4,6,8,10}.

3x-9=12
y^2-5y-11=13

Answer 1

3x-9=12
3x = 12+9
3x = 21
x = 7 , which is a member of your solution set

y^2 - 5y - 11 = 13
y^2 - 5y - 24 - 0
(y-8)(x+3) = 0
y = 8 or y = -3

only y=8 is a solution, since -3 is not part of your solution set.

Answer 2

so i don't have to plug in each number?

Answer 3

yes, you could do that.

I don't know what grade level you are at.
The second question involved solving a quadratic.
If you don't know what that is, then plugging in each value of the replacement set would be your way of doing it.