a)(√20-√30)/√10 |×√10
=(√200-√300)/10
=(10√2-10√3)/10
=[10(√2-√3)]/10
=√2-√3
b)(√18-√12)/√24 |×√24
=[√24(√18-√12)]/24
=[2√6(3√2-2√3)]/24
=(6√12-4√18)/24
=(6×2√3-4×3√2)/24
=(12√3-12√2)/24
=12(√3-√2)/24
=(√3-√2)/2
c)1/√2+√3/√6
=√2/2+√18/6
=(√2×3+√18)/6
=(3√2+3√2)/6
=6√2/6
=√2