the ratio of 50 and a number added to the quotient of a number and 10

the ratio of 50 and a number added to the quotient of a number and 10

Take this algebraic expression in parts.

The phrase a number means an arbitrary variable, let's call it x.
x

The ratio of 50 and x means we divide by 50 by x
50/x

The quotient of a number and 10 means we have a fraction:
x/10

The phrase added to means we add 50/x to x/10
50/x + x/10