(10√1/5+2/3√20)-(5/4√4/5-3/7√245)=10√(1/5)+2/3√20-5/4√(4/5)+3/7√245=10√(5/5²)+2/3√(2²×5)-5/4√[(2/5)²×5]+3/7√(7²×5)=10×(√5)/5+(2/3)×2√5-5/4×2/5×√5+(3/7)×7√5=2√5+(4√5)/3-(√5)/2+3√5=5√5+(4√5)/3-(√5)/2=(30√5+8√5-3√5)/6=(35√5)/6