Let's identify what we are looking for in terms of variables. Sandwiches are s and coffee is c. Casey buys 3 sandwiches, which is represented then by 3s, and 5 cups of coffee, which is represented by 5c. Those all put together on one bill comes to 26. So Casey's equation for his purchases is 3s + 5c = 26. Eric buys 4 sandwiches, 4s, and 2 cups of coffee, 2c, and his total purchase was 23. Eric's equation for his purchases then is 4s + 2c = 23. In order to solve for c, the cost of a cup of coffee, we need to multiply both of those bolded equations by some factor to eliminate the s's. The coefficients on the s terms are 4 and 3. 4 and 3 both go into 12 evenly, so we will multiply the first bolded equation by 4 and the second one by -3 so the s terms cancel out. 4[3s + 5c = 26] means that 12s + 20c = 104. Multiplying the second bolded equation by -3: -3[4s + 2c = 23] means that -12s - 6c = -69. The s terms cancel because 12s - 12s = 0s. We are left with a system of equations that just contain one unknown now, which is c, what we are looking to solve for. 20c = 104 and -6c = -69. Adding those together by the method of elimination (which is what we've been doing all this time), 14c = 35. That means that c = 2.5 and a cup of coffee is $2.50. There you go!

3 0

2 years ago

Los angeles is 1,744 miles from chicago; chicago is 714 miles from new york; and new york is 2,451 miles from los angeles. The t

klemol [59]

Answer:

170°

Step-by-step explanation:

Let a be the distance from Los Angeles to Chicago = 1744 miles, b be the distance from Chicago to New York = 714 miles and c be the distance from New York to Los Angeles = 2451 miles.

A is the angle opposite to side a, B is the angle opposite to side b and C is the angle opposite to side c.

Therefore the angle at Chicago is C.

From cosine rule:

c² = a² + b² - 2ab × cos (C)

2ab × cos (C) = a² + b² - c²

cos (C) = (a² + b² - c²) / 2ab

Substituting:

cos (C) = (1744² + 714² - 2451²) / 2×1744×741

cos (C) = -0.986

C = cos⁻¹ (- 0.986) = 170°

3 0

2 years ago