Is it possible for a triangle to have the side lengths of 3, 8, and 13

No

Step-by-step explanation:

The longest side of a triangle must be less than the sum of the shorter two sides.

3 + 8 = 11.  13 is not less than 11.  So it is not possible for a triangle to have these sides.

5x+40

5(x + 8)

7x - 49

7(x - 7)

18x + 9

9(2x + 1)

15x - 10

5(3x - 2)

step-by-step explanation:

for number one all you have to do is factor 5 out of 5x + 40

for number 2 factor 7 out of 7x - 49

for number three factor 9 out of 18x + 9

for number four factor 5 out of 15x - 10

is means division by fractions

step-by-step explanation: