Question

Keiko sold less than three fourths of his sister's sales

Answer 1

The correct question is
Keiko sold 3 less than three-fourths of his sister’s sales. Which expression represents what Keiko sold?

Let
S----------------> the amount that Keiko's Sister sold
K----------------> the amount that Keiko sold

we know that
Keiko sold 3 less than three-fourths of his sister’s sales
K=(3/4)*S-3

the answer is
K=(3/4)*S-3