Combine like terms: 3x + 7 - 5x + 8 - 7y + 10y

The area of a 25-inch tv screen is 300 square inches. the area of a 40-inch tv screen is 768 square inches. the are of the smaller screen is what percent of the area of the larger screen?

Iam trying to solve a linear equation for the shoe size of someone 84" tall taking into consideration example 1 is 69" tall with a shoe size of 9 and example 2 is 72 inches tall with a shoe size of 11. i understand that the equation should be y=mx+b and that on the graph the answer is (3,2) but i just don't understand how to create the equation to solve for 84-inches and 60-inches tall questions. after two days, i need .

Agroup of three friends order a combo meal which includes two slices of pizza and a drink each drink is priced at $2.50 the combined total of $31.50 how much is the cost of a slice of pizza