Alex was thinking of a number. Alex doubles it and adds 0.9 to get an answer of 21.2. Form an equation with x from the information.

2x + 0.9 = 21.2

Step-by-step explanation:

Let x be the number

The number was doubled so it should be 2x, then add 0.9 equals to 21.2

 2x + 0.9 = 21.2

and x = 10.15

Step-by-step explanation:

30

step-by-step explanation:

idk

i hope i

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!