Unknown variables question

I have a math query relating to a calculation I'm required to do on a property auction website. Apologies if this is the incorrect forum but my understanding of different types of math is quite lacking!

I have the following equation:

w = 200,000

x = 5% of 200,000

y = 17.5% of x

z = x + y

w + z = a

I now need to reverse this equation.

m = w + z. m is known, w and z are unknown.

Both variables to the right of the = are unknown but the percentages are constant, even so, surely this is impossible?

Thanks in advance,

cassiuscoal