👉🏼Make y the subject of

👈🏼Solve the following simultaneous equations:

x^{2}+y^{2}=1

x + 2y = 1

👆🏼Calculate

👇🏼A group of 5 girls and 25 boys sit a test. The mean average mark for the whole class is 82. The mean average mark for the boys is 84. Calculate the mean average mark for the girls.

🖐🏼. Work out f^{-1}(x).