Let f and b be the cost of foil and batteries respectively. We are first given that:
2f+3b=21 subtract 3b from both sides
2f=21-3b divide both sides by 2
f=(21-3b)/2
Then we are given:
5f+2b=25, using f found above in this equation gives you:
5(21-3b)/2+2b=25
(5(21-3b)+4b)/2=25 multiply both sides by 2
5(21-3b)+4b=50 carry out indicated operations on left side
105-15b+4b=50 combine like terms on left side
105-11b=50 subtract 105 from both sides
-11b=-55 divide both sides by -11
b=5, since f=(21-3b)/2
f=(21-3*5)/2
f=3
So batteries cost $5 and foil cost $3.
For every minute you exercise you burn 8.5 calories. It's a linear pattern, so the graph would be a line.
The more minutes you exercise, the more calories you burn, so the graph would rise from left to right.
The number of minutes and the number of calories can't be negative numbers, so the graph would be only in the first quadrant.
The larger the number of minutes, the more calories you would burn.
The answer is D.
The answer to this is .960
