When a tree was planted it was 3 ft tall. Since then, it has been growing at a rate of 0.25 ft per year. How long will it take for the tree to grow to be 15 ft yall?

Just by using basic algebra you can find the answer by saying 0.25 ft every year which in a fraction would be 0.25 ft / 1 year = 15 ft / x. Cross multiply so it becomes 0.25x = 15 ft. Divide 15 ft by the 0.25 ft by bringing it to the other side of the equal sign, 15/0.25 = 60 years