What is the price of tea if person A bought 3 teas and 2 coffees which costed 20.40$ and person B bought 2 teas and 4 coffee for 15.60$?

Answer 1

A; 3T + 2C = 20.40

B: 2T + 4C = 15.60

Subtract B from A

T = 4.80

You continue from here.

Answer 2

Let t = tea and c = coffee

Your two equations are

3t + 2c = 20.40 AND 2t + 4c = 15.60

To use the substitution method, solve the right hand equation for t (you can start with either of them)

2t + 4c = 15.60

-4c -4c

2t = 15.60 - 4c

divide all by 2

t = 7.80 - 2c

substitute this value for t in the left hand equation and solve for c

3t + 2c = 20.40

3(7.80 - 2c) + 2c = 20.40

23.40 - 6c + 2c = 20.40

23.40 - 4c = 20.40

-23.40 -23.40

-4c = -3.00

c = 0.75

substitute the value of the coffee in either of the original equations and solve for t

2t + 4c = 15.60

2t + 4(0.75) = 15.60

2t + 3.00 = 15.60

-3.00 -3.00

2t = 12.60

t = 6.30

Check it (in part because that coffee is too cheap & that tea is too expensive!)

3t + 2c = 20.40

3(6.30) + 2(0.75) = 20.40

18.90 + 1.50 = 20.40