the cost of 3 doughnuts and 5 cups of coffee is 9.90 but 2 doughnuts and 3 coffees cost 6.15 Find the cost of 1 doughnut and 1 cup of coffee. )equations/solution required)

Question

lgbasallote · Answer

let x be doughnuts and y be coffee so..

3x + 5y = 9.90

and 2x + 3y = 6.15

make sense?

anonymous · Answer

Dang, I could go for some doughnuts and coffee right now . . .

anonymous · Answer

i don't know how to solve the equation. help me

anonymous · Answer

It's a system of equations: 2 equations with 2 unknowns. You'll have to substitute one into the other to do it.

anonymous · Answer

i don't know how to it

anonymous · Answer

OK, I'm going to multiply everything by 100 cents/$ to get rid of the decimals (I don't like decimals). I'm going to call doughnuts, 'D' and coffee, 'C'.

300D+500C=990
200D+300C=615

anonymous · Answer

Solve the first equation for C in terms of D and solve the second equation for D in terms of C.

anonymous · Answer

Can you do that much? After that, substitute the expression for C into the equation for D.

anonymous · Answer

sorry i just have a learning disability so I'm struggling.

anonymous · Answer

Should look like this:
$$C=\frac{990-300D}{500} \space , \space D=\frac{615-300C}{200}$$

anonymous · Answer

thank you

anonymous · Answer

You can substitute C into D to get a number for D, then put that number back into the equation for C to get a number for C.