As per PEMDAS rule, we need to evaluate exponential followed by divsion and addition.
Let's simplify first by expanding each terms.
√20+√10√8512=√20+√2×5√2×2×2√5
(canceling the common terms)
=√20+√5√2×2√5=√4×5+√52√5=2√5+√52√5
(taking √5 as common term)
=√5(2+12)√5
(canceling √5 from numerator and denominator)
=2+12
=2.5