How many 5-digit numbers can be formed out of the digits 0, 1, 2, 3, 3, 4,

Twenty-five percent of the customers entering a grocery store between 5 p.m. and 7 p.m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.

2x minus y equals 6, x plus y equals negative 3

Find the maximum value of p= 4x + 5y subject to the following constraints :