The denominators are the same, so add the numerators:

\( \dfrac{1}{4} + \dfrac{3}{4} = \dfrac{4}{4} = 1 \).

Answer: 1.

Write \( \dfrac{2}{5} \) with denominator 10:

\( \dfrac{2}{5} = \dfrac{4}{10} \).

Now add:

\( \dfrac{4}{10} + \dfrac{1}{10} = \dfrac{5}{10} = \dfrac{1}{2} \).

Answer: \( \dfrac{1}{2} \).

Use a common denominator of 24:

\( \dfrac{3}{8} = \dfrac{9}{24}, \quad \dfrac{1}{6} = \dfrac{4}{24} \).

Add:

\( \dfrac{9}{24} + \dfrac{4}{24} = \dfrac{13}{24} \).

Answer: \( \dfrac{13}{24} \).

Use a common denominator of 36:

\( \dfrac{5}{12} = \dfrac{15}{36}, \quad \dfrac{7}{18} = \dfrac{14}{36} \).

Add:

\( \dfrac{15}{36} + \dfrac{14}{36} = \dfrac{29}{36} \).

Answer: \( \dfrac{29}{36} \).

Convert to improper fractions:

\( 2\dfrac{1}{3} = \dfrac{7}{3}, \quad 1\dfrac{2}{3} = \dfrac{5}{3} \).

Add: \( \dfrac{7}{3} + \dfrac{5}{3} = \dfrac{12}{3} = 4 \).

Answer: 4.

Convert to improper fractions:

\( 1\dfrac{1}{4} = \dfrac{5}{4}, \quad 2\dfrac{2}{3} = \dfrac{8}{3} \).

Use a common denominator of 12:

\( \dfrac{5}{4} = \dfrac{15}{12}, \quad \dfrac{8}{3} = \dfrac{32}{12} \).

Add: \( \dfrac{15}{12} + \dfrac{32}{12} = \dfrac{47}{12} \).

Answer: \( \dfrac{47}{12} \).

Use a common denominator of 10:

\( \dfrac{3}{5} = \dfrac{6}{10}, \quad \dfrac{7}{10} = \dfrac{7}{10}, \quad \dfrac{1}{2} = \dfrac{5}{10} \).

Add: \( 6/10 + 7/10 + 5/10 = 18/10 = 9/5 \).

Answer: \( \dfrac{9}{5} \).

Convert the mixed number:

\( 4\dfrac{3}{5} = \dfrac{23}{5} \).

Use a common denominator of 15:

\( \dfrac{23}{5} = \dfrac{69}{15}, \quad \dfrac{2}{3} = \dfrac{10}{15} \).

Add: \( \dfrac{69}{15} + \dfrac{10}{15} = \dfrac{79}{15} \).

Answer: \( \dfrac{79}{15} \).

Add the distances:

\( \dfrac{2}{3} + \dfrac{3}{5} \).

Use a common denominator of 15:

\( \dfrac{2}{3} = \dfrac{10}{15}, \quad \dfrac{3}{5} = \dfrac{9}{15} \).

Add: \( 10/15 + 9/15 = 19/15 \).

Answer: \( \dfrac{19}{15} \) km.

Convert the mixed number:

\( 1\dfrac{1}{2} = \dfrac{3}{2} \).

Add: \( \dfrac{3}{2} + \dfrac{3}{4} \).

Use a common denominator of 4:

\( \dfrac{3}{2} = \dfrac{6}{4} \).

So \( \dfrac{6}{4} + \dfrac{3}{4} = \dfrac{9}{4} \).

Answer: \( \dfrac{9}{4} \) hours.