50 ! whoever is the first to answer out of two people gets marked as brainliest! determine best method to solve each system of equations. 19.) x + y = 2 20.) - x - 5y = 7 y = 2x - 1 x + y = 1 21.) 3x + y = 26 22.) 4x - 8y = 52 3x + 3y = 26 7x + 4y = 1

19 substitution

20 elimination

21 elimination

22 elimination

Step-by-step explanation:

19.) x + y = 2

y = 2x - 1

Substitution, since the second equation is already solved for y

x + (2x-1) =2

Combine like terms

3x-1 =2

Add 1 to each side

3x-1+1= 2+1

3x=3

Divide by 3

x=1

Now we need y

x+y =2

1+y= 2

Subtract 1

y=1

(1,1)

20.) - x - 5y = 7

x + y = 1

I will used elimination since  there is an x and a -x

- x - 5y = 7

x + y = 1

-4y = 8

Divide by -4

-4y/-4 = 8/-4

y = -2

x+y =1

x-2=1

Add 2 to each side

x-2+2=1+2

x=3

(3,-2)

21.) 3x + y = 26

3x + 3y = 26

I will use elimination by multiplying the second equation by -1

3x + y = 26

-3x - 3y = -26

   -2y = 0

Divide by -2

-2y/-2 = 0/-2

y =0

Now we need to find x

3x + 0 = 26

Divid by 3

3x/3  = 26/3

x = 26/3

(26/3 ,0)

22.) 4x - 8y = 52

7x + 4y = 1

I will use elimination by multiplying the second equation by 2

2( 7x + 4y = 1 )

14x +8y =2

The add this to the first equation to eliminate y

4x - 8y = 52

14x +8y =2

18x = 54

Divide by 18

18x/18 = 54/18

x=3

Now we need to find y

7x + 4y = 1

7(3) +4y = 1

21 +4y = 1

Subtract 21 from each side

21-21 +4y = 1-21

4y = -20

Divide by 4

4y/4 = -20/4

y=-5

(3,-5)

7 weeks

step-by-step explanation:

convert each fraction to the least common multiple of 20, so 3/4 = 15/20 & 1/10 = 2/20, then divide 15 by 2 and you get a little over 7, so the food will last 7 weeks.

answer:  

step-by-step explanation:

here x represents the height of the pole,

and, the height of the shadow of the pole is 12 feet.

also, the angle of elevation from the top of the pole is 40°,

therefore,

by the low of sine,

which is the required equation for finding the value of x,