Solve for x assume that lines which appear tangent are tangent

Tree diagram to find the prime factors of 18

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

What is the inverse of the function f(x) = 2x + 1?