Упростим выражение:
1) $$ \frac{2}{15}b + \frac{3}{12}b = \frac{2}{15}b + \frac{1}{4}b = \frac{2 \cdot 4 + 1 \cdot 15}{60}b = \frac{8 + 15}{60}b = \frac{23}{60}b $$.
2) $$ \frac{14}{24}a - \frac{3}{16}a = \frac{7}{12}a - \frac{3}{16}a = \frac{7 \cdot 4 - 3 \cdot 3}{48}a = \frac{28 - 9}{48}a = \frac{19}{48}a $$.
Ответ: 1) $$\frac{23}{60}b$$; 2) $$\frac{19}{48}a$$