First you need to combine like terms. The like terms in this is 7y & 3y and -9 & 19. So to combine those like terms, you first need to subtract 3y on both sides because to cancel out the 3y in the right side, you need to perform the opposite operation on the positive 3. And 3y - 3y is 0 so thats why you subtract 3y on both sides. When you subtract 3y from 7y on the left side (because 3y is the like term of 7y and what operation you do on one side you have to do on the other side of the equation) you get 4y - 9 = 19. Now you still need to combine the like terms -9 and 19 so you need to add 9 on both sides to get 4y = 28. Since 4 is being multiplied by "y" to get "y" by itself in the left side of the equation, you need to divide 4 on both sides. 28 ÷ 4 = 7, so your final answer would be y = 7!
To find the tax rate when given the initial price of an object and the final tax value, you use the equation: $350 * X = $22.75 (where X is the sales tax rate). Then solve: $22.75/$350 = .065
