Tính

a, 17201720 : 2,7+2,7:1,35+(0,4:212212 ) . (4,2-13401340 )

b, (635−3314).556:(21−1.25):2,5(635−3314).556:(21−1.25):2,5

c,0,125−15+170,375−35+37+12+13−0,234+0,5−310