Question 385310
It appears as if you have three variables, but if you keep reading the question, you'll see you can actually express the three lengths in terms of the first.


We know the 3 lengths add up to 40. 


Let's let x = the first length


We also know the second length is 4 times the first, so the second length is 4x. That means the third length must be 3x. Putting it all together:


x + 4x + 3x = 40
8x = 40
x = 40/8
x = 5


So the first length is 5 inches.


The second length is 5*4 = 20 inches
The third length is 3*5 = 15 inches.


Check that the three lengths add up to 40:


5+15+20 = 40


Yes, it works! Good job you're done.