Since if he gets the driveway done in 20 minutes he gets 1/20th of the driveway done in 1 minute (if x=20 then x/20=1 by dividing both sides by 20) and if his brother gets 1/12th of the driveway done in one minute, then if t represents the time it takes to shovel the driveway, t/20+t/12=1 driveway shoveled as 1/20+1/12=amount they can do in 1 minute, so t/20+t/12 is how much they can do in t minutes. Multiplying both sides by 20*12=240, we get 12t+20t=32t=240. Dividing both sides by 32, we get 240/32=7.5 minutes to shovel the driveway.
Your answer is a Square Pyramid.
(Hope I helped :C
Point slope form is
y-y1=m(x-x1)
where slope=m
and (x1,y1) is a given point
slope=(y2-y1)/(x2-x1)
slope=(6-7)/(-8-(-5))=-1/(-8+5)=-1/-3=1/3
pick any point
(x,y)
(-5,7)
y-7=1/3(x+5) or
y-6=1/3(x+8)
