let h= history books
science books = s
h=2s there are 2 times as many history as science so to get them equal we double the science
h+s=81 there are 81 total history and science books
2s+s=81 substitute 2s for h in the above equation
3s = 81 combine like terms
s = 27
There are 27 science books
h=2s
h=2(27)
h=54
there are 54 history books
Answer:
H - 6x^7y^15
Step-by-step explanation:
Volume of a rectangular prism (box) is l x w x h
3x^2y^4 * 4x^2y^5 * 1/2x^3y^6
= 6x^7y^15
Jenny average swimming speed was 2.5 km/h, her average biking speed was 24 km/h and her average running speed was 12 km/h.
<h3>Speed</h3>
Speed is the ratio of total distance travelled to total time taken. It is given by:
Speed = distance / time
Let a represent the average swimming speed, b the average biking speed and c the average running speed.
Her average biking speed was 2 times her average running speed, hence:
Her average running speed was 8 times her average swimming speed. Hence:
Total distance of the triathlon was 55.5 kilometers. Hence:
a * 1 hour + b * 1.75 hour + c * 1 hour = 55.5 (3)
From equation 1, 2 and 3:
a = 2.5, b = 24, c = 12
Jenny average swimming speed was 2.5 km/h, her average biking speed was 24 km/h and her average running speed was 12 km/h.
Find out more on speed at: brainly.com/question/6504879
Answer:
27 and 23
Step-by-step explanation:
x + y = 50
x - y = 4
2x = 54
x = 27
y = 23
