Suppose 40 bikes stand near a playground. Some of them are bicycles, some of them are tricycles, and two of them have four wheels. John counts all the wheels and gets 100, in total. How many tricycles are there?

16 tricycles

Step-by-step explanation:

First, let's make a chart:

Bicycles- x bicycles and 2x wheels

tricycles- y tricycles and 3x wheels

Four wheeled vehicles- 2 bikes (given), 8 wheels

Since the total amout of bikes is 40, that means that x+y+8=40

You can simplify that to x+y=38.

now, we're going to form another equations dealing with the number of wheels.

Since we know that four wheeled vehicles already have only 8 wheels, then that means 2x+3y=92

Solve the system of equations:

2x+3y=92

x+y=38

y will be 16

Step-by-step explanation:

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!