The price of salt goes up by 9 cents. The old price goes up by four-fifth of new prices. Find old and new price.

Answer 1

old price --- x
new price ----x+9

increase in old price = (4/5)(x+9)
new price = x+ (4/5)x+9)

x+9 = x + (4/5)(x+9)
9 = (4/5)(x+9)
45 = 4x + 36
4x = 9
x = 9/4 cents ?? or 2.25 cents

check:
old price -- 2.25 cents
new price --11.25 cents

other way to get new price:
increase in old price = (4/5)(11.25) = 9
new price = 2.25+9 = 11.25

my answer works for the wording given.
Is this taken from a mathbook from the 1920's ??
Very strange wording besides the unreasonable numbers