Answer:
a = length
b = height(width)
a=3b
2(a+b)=120
2(b+3b)=2(4b)=8b
8b=120
b=15
a=45
length is 45 feet
width is 15 feet
7/16 of a yard
Step-by-step explanation:
Let's put the boards to the same denominator so it's easier.
Let's go with a denominator of 16
1/4= 4/16
7/8= 14/16
3/16 stays the same.
So, 4/16+3/16+x=14/16
7/16+x=14/16
x=7/16 of a yard, the length of the 3rd board.
B