If the y-intercept of the graph is 2x + by = 15 is 5, what is the value of b?

First you have to subtract 2x
by=15-2x then divide by y
b=15-2x/y < that's your answer 

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's