5x-15y=-20, 5x-4y=-9 systems of equations (elimination)

(- 1, 1 )

Step-by-step explanation:

5x - 15y = - 20 → (1)

5x - 4y = - 9 → (2)

Multiplying (2) by - 1 and adding to (1) will eliminate the x- term

- 5x + 4y = 9 → (3)

Add (1) and (3) term by term to eliminate x

0 - 11y = - 11

- 11y = - 11 ( divide both sides by - 11 )

y = 1

Substitute y = 1 into either of the 2 equations and solve for x

Substituting into (1)

5x - 15(1) = - 20

5x - 15 = - 20 ( add 15 to both sides )

5x = - 5 ( divide both sides by 5 )

x = - 1

solution is (- 1, 1 )

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40

question: how many people can she serve?

answer: she can serve 16.66666667 people. so she can only give 16 people a complete serving.

question: does she have enough ice cream for her guests?

answer: no. explanation: she only has enough for 16 people to have a full serving. however, she can give a 17th person a partial serving.