You need a 30% alcohol solution. On hand, you have a 780 mL of a 15% alcohol mixture. You also have 90% alcohol mixture. How much of the 90% mixture will you need to add to obtain the desired solution?

You will need mL of the 90% solution?

PLEASE HELP!!! BRAINLIEST! FOR MY FINAL!!!

195 mL of the 90% solution

Step-by-step explanation:

Let the number of mL of 90% mixture = x

Hence, our equation is

780mL × 15% + x mL × 90% = (780mL + x) 30%

117 + 0.9x = 234 + 0.3x

Collect like terms

0.9x - 0.3x = 234 - 117

0.6x = 117

x = 117/0.6

x = 195 mL

Therefore, You will need 195 mL of the 90% solution

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!

if you are looking for the unit rate then the answer would be 9 because unit rate is distance divided by time.

step-by-step explanation: