What is the formula for calculating the operands of the sum of a number and its percentage?

Question

Mathematics

Hey!
x=100;
y = 20% of x = 20; (percentage may be different, but it is known in advance)
z = x + y = 120

What formula is used to calculate x and y if only their sum = z and the interest rate p = 20% are known ?
z = x + y = 120
p = 20 (percentage may vary and is known in advance)
y = (x/100)*p

x = ?
y=?

Answer 1

Proportions now pass in the third grade or in the second?
100+p --- z
100 --- x
p --- y
x=100*z/(100+p)
y=p*z/(100+p)