Question

Can someone please help me with this problem asap? Thanks!! :))

Answer 1

Answer: $\ 4.34$

Step-by-step explanation:

We have the following information:

Fredburguer $F$, milkshake $M$ and an order of fries $f$ costs $\ 3.72$:

$F+M+f=\ 3.72$ (1)

One Fredburguer is equal to a milkshake plus orders of fries:

$F=M+2f$ (2)

Three milshakes is equal to a Fredburguer plus an order of fries:

$3M=F+f$ (3)

And we are asked: If we have a Fredburguer, a milkshake and two orders of fries, how much do we have to pay?

$F+M+2f=x$ (4)

Well with the first three equations we have a system of equations to solve. Let's begin by isolating $F$ from (3):

$F=3M-f$ (5)

Making (2)=(5):

$M+2f=3M-f$ (6)

Isolating $f$:

$f=\frac{2}{3}M$ (7)

Substituting (7) in (2):

$F=M+2(\frac{2}{3}M)$ (8)

Isolating $F$:

$F=\frac{7}{3}M$ (9)

Substituting (7) and (9) in (1):

$\frac{7}{3}M+M+\frac{2}{3}M=\ 3.72$ (10)

Isolating $M$:

$M=\ 0.93$ (11) This is the cost of a Milkshake

Substituting (11) in (7):

$f=\frac{2}{3}\ 0.93$ (12)

$f=\ 0.62$ (13) This is the cost of an order of frieds

Substituting (11) in (9):

$F=\frac{7}{3}\ 0.93$ (14)

$F=\ 2.17$ (15) This is the cost of a Fredburguer

Substituting (11), (13) and  (15) in (4):

$\ 2.17+\ 0.93+2(\ 0.62)=x$ (16)

Finally:

$x=\ 4.34$ This is the cost of a Fredburguer, a milkshake and two orders of fries