5x+2y=9 , and 5x+10y=75

There is no question stated here so I will improvise.

Step-by-step explanation:   Time Stamp ( 6  9  10  16)

5x+2y=9

5x+10y=75     substract these two equations

0x - 8y = -66

 -8y  = -66

    y  =  -66/-8

    y  =  8.25

5x+2y=9

5x+2(8.25)=9

 5x  = 9 - 16.5

   x  =  -7.5 / 5

   x  = -1.5

problem:

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

f(5/2) = 10/3

i hope this !

step-by-step explanation:

i'm pretty sure it would take 20 hours because it's half the men so you multiply the number of hours it takes by 2