Answer:
This problem can be solved by working backwards.
Average of 30 students = 70.
Total marks of all the 30 students = 30x70 = 2100
Out of these 30, average of 20 students = 62
Total marks of these 30 students = 30x62 = 1860
So the total marks of the remaining 10 students = 2100-1860 = 240
Hence the average of the remaining 10 students = 240/10 = 24
So standard form is Ax+By=C
Since the problem is already in that form you don’t need to switch it around however A has to be more than 0 (so positive). Divide the equation by -3 to get the answer x-4y=-8
To find the original price, add the discount back onto the sales price.
17.55+5.85= 23.4
So your answer would be $23.40. Hope this helps!
