Answer:
D
Step-by-step explanation:
The basic equation to solve this would be D = RT, which is
D is Distance
R is Rate (speed)
T is time
To find total distance D, we can find individual distances for two legs of the whole.
First Leg:
R = 8
T = a
D = 8a
Second Leg:
R = 7.5
T = b
D = 7.5b
Total distance D is:
D = 8a + 7.5b
Moreover, we know student runs 45 minutes in total hence a + b = 45 or we can say a = 45 - b, so we can replace this in the equation found:
D = 8a + 7.5b
D = 8(45 - b) + 7.5b
Answer choice D is right.
A) 6+x+4 = 2+3x+4
10+x = 3x+6
10 = 2x+6
4 = 2x
x = 4/2
x = 2
B)
6 * (x+4) = 2 *(3x+4) =
6x+24 = 6x+8
there is no solution for part B
Lynn mixes 39 pounds of water with 48 pounds of brick dust, so the mixture has a total weight of 39 + 48 = 87 pounds.
13 pounds are spilled during mixing, so she's left with 87 - 13 = 74 pounds to turn into bricks.
7 pounds are needed for 1 brick, so she can make 10 bricks because 7 • 10 = 70 and 7 • 11 = 77, and 70 < 74 < 77.
If she uses the mixture to make 10 bricks, she uses up 70 pounds of it, which leaves 4 pounds to be washed out.
