Directions are simplify by combining like terms.

x radiacal 18 -3 radical 8x^2

can someone show me how to do these types of problems. thanks

I cant determine the second term. For the first, I think you meant

x sqrt(18) which reduces to
x sqrt (9*3) or
3x sqrt 3

First remove squares from under the radical sign
x sqrt(18) = x sqrt (9*2) = 3x sqrt 2
and
3 sqrt(8x^2) = 3 sqrt (4*2*x^2)
= 6x sqrt 2
Now combine terms.
x sqrt(18) - 3 sqrt(8x^2)
= sqrt 2*(3x - 6x) = -3x sqrt 2

You can get other possible answers by using the negative square roots. For example
x sqrt(18) = x sqrt (9*2)
= (+ or -) 3x sqrt 2