The difference of a square of a number and 12 is equal to four times that number

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog

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

You’re ordering more thread for blue jeans co. you usually purchase from ted’s threads, which sells 12 thread spools for $27. you recently received a notice from wade's wares that says you can buy thread from them for $2.30 each for the first 2 dozen and $2 a spool thereafter. you need to order 5 dozen spools. what percentage can you save by going with wade’s wares?