State an equation you could use to find the value of x. then find the value of x in simplest form.

You can use the Pythagorean Theorem:

a^2+b^2=c^2
x^2+x^2=(7√2)^2
2x^2=49*2 (combine like terms and square the 7√2)
x^2=49 (divide both sides by 2)
x=7 (square root both sides)

So the equation is 2x^2=98 (simplest form) and x=7

Hope this helps