Answer:
Determine whether the equation is half or double the given number, then solve for x.
Explanation:
The hash marks on the sides of the triangles tell you that the pieces of the triangles are the same length. The piece with one mark is the same length as the other piece with one mark. The piece with two marks is the same length as the other piece with two marks.
This is important because it tells you that the place where the triangle is divided is at its halfway point — so, the triangles are cut right in half. The line that cuts the triangle in half will always be half the length of the line that is the bottom of the triangle. You can use this to solve for x in each of these problems.
Examples:
12) We are trying to solve for x along the length of the longer line. The halfway-point line is seven.
Seven is half of fourteen (7*2=14). So, the longer line is 14.
Since the longer line has the equation 2x, we must determine what times two is fourteen. To find that, we would divide fourteen by two (division and multiplication are inverse operations). 14/2=7.
x=7.
15) We are trying to solve for x along the length of the shorter line. The longer line is 35.
The shorter line is half of the longer line, so in this case it is half of 35, which is 17.5.
However, in the equation, we subtract 8 from x. So, we have to find the number that becomes 17.5 only after you subtract 8. To do this, you simply add 8 to 17.5 (addition and subtraction are inverse operations). 25.5 - 8 = 17.5.
x = 25.5.