3分之10乘7分之3加3分之20乘7分之3用简便方法算 还有5分之19乘9乘分之1加5分之1除以9用简便计算要写出过程

10/3 * 3/7 + 20/3 * 3/7
= (10/3 + 20/3) * 3/7
= 30/3 * 3/7 = 30/7
19/5 * 1/9 + 1/5 / 9
= 19/5 / 9 + 1/5 / 9
= (19/5 + 1/5) /9
= 20/5 / 9
= 4/9