X=1/2 and 3/2 do on paper. Have you tried entering them as 0.5 and 1.5?.
1 ) Billy walks 15 miles every day to soccer practice and he had 5 practices last week.
We know that, 1 mile = 1760 yards
So, 15 miles = (15× 1760) yards = 26400 yards
Thus the total distance walked in 5 practices will be: 
2) Mark's current age is
years
So, his age was in 10 years ago 
Given that, his current age is 3 times his age 10 years ago.
So, the equation to represent this situation will be : 
Answer:
132
Step-by-step explanation:
f(1) = 9
f(n) = -4f(n-1) + 4
Let n = 2
f(2) = -4f(2-1) + 4 = -4 f(1) +4 = -4(9) +4 = -36+4 = -32
Let n = 3
f(3) = -4f(2-1) + 4 =-4f(2)+4 = -4 (-32) +4 = 128+4=132
To find the percent of the birdhouses occupied, divide the number of occupied birdhouses by how many birdhouses there are in total:

Convert this decimal into a percentage by multiplying by 100:
5.26% of the birdhouses are occupied.