Answer:
2/5
Step-by-step explanation:
She completed 8 out of 20 so we divide 8 by 20
8/20 can be simplified if we divide both the numerator and denominator by 4
which equals 2/5
a function can't have one input mapped to multiple outputs. this is the case for where 4 maps to -2 and 2, so remove (4, -2)
If we want to calculate the full prize we need to calculate how much the tax was:
420* 17

%=420*

=420*

=21*

=73.5
so this is how much the tax was.
and the full prize is the cost of the ring and the tax: 420+73.5=493.5
so that's how much the buyer will pay
5/4 - square root of 3 = -0.48