A= 2 and b=4 then 27-b2 ÷a+(11-5) is equal to?

I would use PEMDAS. I'm not so sure if this is right but I hope it helps.
27-(4)*2/(2)+(11-5)
27-(4)*2/(2+(6)
27-8/(2)+(6)
27-4+6
27-10=17

Substitute the variables with the numbers.. and I think you use the order of operations, which is PEMDAS :
27 - (4)(2) ÷ 2 + (11-5)
P = Parentheses first : 27 - (4)(2) ÷ 2 + 6
E = Exponents second : There are no exponents, so continue to the next step :
M = Multiplication third : 27 - 8 ÷ 2 + 6
D = Division fourth : 27 - 4 + 6... ( 8 ÷ 2 = 4 )
S = Addition and subtraction are the same order just like multiplication and Division, so you do the operation from left to right; subtraction is the next step :
27 - 4 + 6 = ( 27 - 4 = 23 )
And finally the last step, which is addition : 23 + 6 = 29
The answer to this question is 29

This was pretty long, lol XD
Hope I helped a little :)

C. i believe it is (5×(-20))+(100×(0.7))