How can you tell an equation is linear? example: 22x-14y=65

Margaret is purchasing a house for $210,000 with a 15 year fixed rate mortgage at 4.75% interest she has made a 5% down payment the house is valued at 205,000 and the local tax rate is 3.5% homeowners insurance 600 per year what are her total monthly payment

What is the perimeter of an isosceles triangle with each leg measuring 2x+3 and the base measuring 6x-2?

Afurniture store is having a weekend sale and is offering a 20% discount on patio chairs and tables the sales tax on furniture is 6.25%