Answer:
(b) -4.5
Step-by-step explanation:
Choosing the correct answer here is not the same as knowing what the correct value is.
Estimate
You know that √30 < √100 = 10, so the sum must be negative. That is, 10 subtracted from a positive number less than 10 will give a negative result.
You know that 25 < 30 < 36, so √25 < √30 <√36. That is, √30 will be between 5 and 6. If we say √30 ≈ 5.5, then the sum is ...
-10 +√30 ≈ -10 +5.5 = -4.5
__
Additional comment
Of course, a calculator can tell you the value to the desired precision.
