Answer:
408 is correct
0.8 x 510 = 408
Explanation:
When we get a sale value or reduced value to find
This is a short cut of workings in bold to find correct value.
10% of 510 = 51
20% of 510 = 102
510-102 =408
17 x 30 = 510 Not correct as calculated before taxes.
100-80/ 100 = 0.8
0.8 x 510 = 408
408/510 = 0.8 Is correct
0(17) (30) = 510 Not correct as calculated before tax
510 - 2(17)(30) = 510 i Not correct as calculated before tax.