An equilateral triangle has a perimeter of 42. What is it's height?

How do you solve a question like this?

Agroup of students want to create a garden. they do not know the exact measurements but they propose using a variable to represent the length and width of the garden. the length of the garden is 10 feet longer than double the width. use a single variable to write algebraic expressions for both the length and width of the garden. write an algebraic expression for the area of the garden. use mathematical terms to describe this expression.

If your teacher tells you to do questions 6 through 19 in your math book for homework, how many questions is that