Can someone solve this problem please?

Connect WY....this will form right triangle  WXY

Since WX = WY....then this will be an isisceles right triangle

And WY  = √[4^2 + 4^2]  = √32  

And angle WYX  = 45

So....in triangle WYZ, angle WYZ =  135 - 45  = 90

So.....triangle WYZ is also a right triangle with WZ being the hypotenuse

So....

a  = √(WZ^2 - WY^2)   = √ ( 9^2  - (√32)^2 ]  = √ [81 - 32]   = √49  =  7

Determine the value of a.

Thanks!!!