PLEASE HELP!
SOLVE { X+Y=4
{7X+9Y=42

Step-by-step explanation:

x + y = 4  (i)

x = 4-y

7x + 9y = 42 (ii)

Plug in x = 4-y in equ (ii)

           7*(4 - y) + 9y = 42

             28 - 7y +9y = 42

                   28 + 2y = 42

                           2y = 42 - 28

                           2y = 14

                            y = 14/2

y = 7

x = 4 - y

x = 4 - 7

x = -3

use system of equations

x+y=4

7x+9y=42

if we want to solve for y first

then multiply the first equation by 7 to cancel out x

 7x+7y=28

- 7x+9y=42

-2y=-14

y=7

to solve for x just input y into the equation

choose any equation u like from one of the two

x+7=4

x=4-7

x=-3

Step-by-step explanation:

given data

mean = 1.9 hours

standard deviation = 0.3 hours

solution

we get here first  random movie between 1.8 and 2.0 hours

so here

P(1.8 < z < 2 )

z = (1.8 - 1.9) ÷ 0.3

z = -0.33

and

z = (2.0 - 1.9) ÷ 0.3

z = 0.33

z = 0.6293

so

P(-0.333 < z < 0.333 )

=  0.26

so random movie is between 1.8 and 2.0 hours long is 0.26

and

A movie is longer than 2.3 hours.

P(x > 2.3)

P(  > )

P (z  >  )

P (z  > 1.333  )

= 0.091

so chance a movie is longer than 2.3 hours is 0.091

and

length of movie that is shorter than 94% of the movies is

P(x > a ) = 0.94

P(x <  a ) = 0.06

so

P( <   )

a = 1.43

so length of the movie that is shorter than 94% of the movies about 1.4 hours.