#### Answer

x= 7$\sqrt 2$

#### Work Step by Step

In a 45$^{\circ}$-45$^{\circ}$-90$^{\circ}$ triangle, both legs are congruent and the length of the hypotenuse is $\sqrt 2$ times the length of the leg. In the diagram, the leg is 7 and the hypotenuse is x, so to solve for x, you would take 7 and multiply it by $\sqrt 2$ and leave it in simplest radical form, getting the answer that x= 7$\sqrt 2$.