Your answer is very close to being correct; however, the true answer is actually

without any parenthesis needed around the fraction. Notice how there is no (x) at the end.
Answer:
Rs. 23520
Step-by-step explanation:
Given that :
At 12% profit ; sales price = 18,816
At (12 + 3)% profit ; sales price = x
Hence,
0.12 = 18,816
0.15 = x
Cross multiply ;
0.12x = 0.15 * 18816
0.12x = 2822.4
x = 2822.4 / 0.12
x = 23520
Hence, sales price for a 3% increaa in profit should be Rs. 23520
Answer:
3/12 and 5/x
12 times 5 is 60 so 3 times 20 shall be 60
3/12 = 5/20
:)