What is the sum of the digits of all
2-digit numbers from 10 to 99?

(99)(100)/2 - (9)(10)/2 = 4905

Fast way to solve: allow leading zero's temporarily, then first digit can be any of 0..9 and so can second digit, so each digit appears 10 times in each position, so sum is 20 * (9)(10)/2, except that we must subtract sum of 1..9, so it's 19 * (9)(10)/2 = 855.

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

answer:

f(5/2) = 10/3

i hope this you!

step-by-step explanation:

first you will have to convert 3/4 into a decimal

which is .75

then you will have to divide 1.5 by .75

which is 2

no you have to divide