There are 4 variables in the expression. The variables are: a,b,c and d.
8d^2 = variable d
2bc = variables b and c
10ab = variables a and b
Any number that you can completely write down on paper using digits ... and a fraction bar or decimal point if necessary ... is a rational number. If you add it to 0.5, then the sum is another rational number.
5 can stay as is, but 5503 can be rounded to 5500 so 5500x5=27500
