He answered 8 questions incorrectly. 2*8=16 100-16=84
Its 30 you find the unit rate by 21÷7 which equals 3 then you multipy 3x10 which gives you 30
To find the inverse, interchange the variables and solve for y.
f^-1 (x) = 4 + x/2
3:15pm hope this helps bff