Вычислите: а) 1/4+3/10; б)3/5-1/6; в)7/10-2/15; г)5/12+3/8

а ) 1 / 4 + 3 / 10 = ( 20 / 4 * 1 + 20 / 10 * 3 ) / 20 = ( 5 * 1 + 2 * 3 ) / 20 = ( 5 + 6 ) / 20 = 11 / 20 ; б ) 3 / 5 - 1 / 6 = ( 30 / 5 * 3 - 30 / 6 * 1 ) / 30 = ( 6 * 3 - 5 * 1 ) / 30 = ( 18 - 5 ) / 30 = 13 / 30 ; в ) 7 / 10 - 2 / 15 = ( 30 /10 * 7 - 30 / 15 * 2 ) / 30 = ( 3 * 7 - 2 * 2 ) / 30 = ( 21 - 4 ) / 30 = 17 / 30 ; г ) 5 / 12 + 3 / 8 = ( 24 / 12 * 5 + 24 / 8 * 3 ) / 24 = ( 2 * 5 + 3 * 3 ) / 24 = ( 10 + 9 ) / 24 = 19 / 24 .