Answer
The length of the table is 90 inches and its width is 30 inches.
Work Step by Step
We assign the variables:
$l=$ length of the table
$w=$ width of the table.
Step 1:
Find the equations that represent the problem.
The formula for the perimeter of a rectangle is $P = 2l+2w$. In this case, the perimeter (the sum of the measurements of the four sides) is 240 inches.
$2l+2w=240$ -> Eq. 1
We can get the second equation from the wording in the problem.
From "The length of the table is 3 times its width", we get:
$l=3w$ -> Eq. 2
Step 2:
Solve the system of equations using the substitution method,
-> Substitute Eq. 2 into Eq. 1
$2(3w)+2w=240$
$6w+2w=240$
$8w=240$
$w=\frac{240}{8}$
$w=30$ inches
-> Substitute the value for $w$ into Eq. 2
$l=3(30)$
$l=90$ inches
Step 3:
The length of the table is 90 inches and its width is 30 inches.
