21 - 4x = 108
<em><u>Subtract 21 from both sides</u></em>
-4x = 87
<em><u>Divide both sides by -4</u></em>
x = -21.75
Answer:
c?
Step-by-step explanation:
The smallest natural number is 1. The largest natural number does not exists because there will always be one even larger. But if you are asking the number of all natural numbers or the size of natural number set then 
is your answer.
Answer:
x= 3/4
Step-by-step explanation:
I looked it up. Hope this helps
Answer:
- train: 40 kph
- plane: 140 kph
Step-by-step explanation:
Let t represent the speed of the train in km/h. Then 4t-20 is the speed of the plane. Travel times are the same, so we can use the formula ...
time = distance/speed
and equate the travel times.
110/t = 385/(4t-20)
Cross multiplying gives ...
110(4t -20) = 385t
440t -2200 = 385t . . . . . eliminate parentheses
55t -2200 = 0 . . . . . . . . . subtract 385t
t -40 = 0 . . . . . . . . . divide by 55
t = 40 . . . . . . . . . . . add 40; train's speed is 40 kph
4t -20 = 140 . . . . . . find plane's speed; 140 kph
The train's speed is 40 km/h; the plane's speed is 140 km/h.
_____
<em>Check</em>
Train's travel time = 110 km/(40 km/h) = 2.75 h.
Plane's travel time = 385 km/(140 km/h) = 2.75 h.
