Răspuns:
5⁴:5²+5•(55¹-x)=5³
5²+5•(55-x)=5³
5•(55-x)=5³-5²
5•(55-x)=125-25
5•(55-x)=100
55-x=100:5
55-x=20
x=55-20
x=35