Which expression can be used to convert 80 US dollars (USD) to Australian dollars (AUD)? 1 USD = 1.0343 AUD 1 AUD = 0.9668 USD 80 U S D times StartFraction 0.9668 U S D Over 1 A U D EndFraction 80 U S D times StartFraction 1.0343 U S D Over 1 A U D EndFraction 80 U S D times StartFraction 0.9668 A U D Over 1 U S D EndFraction 80 U S D times StartFraction 1.0343 A U D Over 1 U S D EndFraction Mark this and return

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.