Question

Zoe bought a bike on sale at 15% off the original price.

Answer 1

$\frac{15}{100}\times420=0.15\times420=63 \\ \\ So \ 420 - 63 =$
$ $357$

Answer 2

$\ 420$ original prize 
$15\%$ discount
$100\%-15\%=85\%$
$85\%=0.85$
$\ 420*0.85=\ 357$