5.445 Вычислите: a) 1/2+1/3; б) 1+2/7; в) 2+1/5; г) 3+4/9; д) 5/9-1/6; e) 3/4-1/3; ж) 6+1/3; з) 9/5-7/10; и) 1/2-3/8; к) 15-3/10; л) 3/8+5/12; м) 5/9-1/6; н) 11+5/3; о) 17-3/30; п) 17-4/15.

а) $$1/2+1/3 = (1 \cdot 3)/(2 \cdot 3) + (1 \cdot 2)/(3 \cdot 2) = 3/6+2/6 = 5/6$$

б) $$1+2/7 = 7/7+2/7 = 9/7 = 1\frac{2}{7}$$

в) $$2+1/5 = 10/5+1/5 = 11/5 = 2\frac{1}{5}$$

г) $$3+4/9 = 27/9+4/9 = 31/9 = 3\frac{4}{9}$$

д) $$5/9-1/6 = (5 \cdot 2)/(9 \cdot 2)-(1 \cdot 3)/(6 \cdot 3) = 10/18-3/18 = 7/18$$

е) $$3/4-1/3 = (3 \cdot 3)/(4 \cdot 3)-(1 \cdot 4)/(3 \cdot 4) = 9/12-4/12 = 5/12$$

ж) $$6+1/3 = 18/3+1/3 = 19/3 = 6\frac{1}{3}$$

з) $$9/5-7/10 = (9 \cdot 2)/(5 \cdot 2)-7/10 = 18/10-7/10 = 11/10 = 1\frac{1}{10}$$

и) $$1/2-3/8 = (1 \cdot 4)/(2 \cdot 4)-3/8 = 4/8-3/8 = 1/8$$

к) $$15-3/10 = 150/10-3/10 = 147/10 = 14\frac{7}{10}$$

л) $$3/8+5/12 = (3 \cdot 3)/(8 \cdot 3)+(5 \cdot 2)/(12 \cdot 2) = 9/24+10/24 = 19/24$$

м) $$5/9-1/6 = (5 \cdot 2)/(9 \cdot 2)-(1 \cdot 3)/(6 \cdot 3) = 10/18-3/18 = 7/18$$

н) $$11+5/3 = 33/3+5/3 = 38/3 = 12\frac{2}{3}$$

о) $$17-3/30 = 510/30-3/30 = 507/30 = 16\frac{27}{30} = 16\frac{9}{10}$$

п) $$17-4/15 = 255/15-4/15 = 251/15 = 16\frac{11}{15}$$

Ответ: а) $$5/6$$, б) $$1\frac{2}{7}$$, в) $$2\frac{1}{5}$$, г) $$3\frac{4}{9}$$, д) $$7/18$$, е) $$5/12$$, ж) $$6\frac{1}{3}$$, з) $$1\frac{1}{10}$$, и) $$1/8$$, к) $$14\frac{7}{10}$$, л) $$19/24$$, м) $$7/18$$, н) $$12\frac{2}{3}$$, о) $$16\frac{9}{10}$$, п) $$16\frac{11}{15}$$