7. add: $2\\frac{2}{3}+3\\frac{3}{4}$

Explanation:

Step1: Convert mixed numbers to improper fractions

$2\frac{2}{3}=\frac{2\times3 + 2}{3}=\frac{6+2}{3}=\frac{8}{3}$，$3\frac{3}{4}=\frac{3\times4+3}{4}=\frac{12 + 3}{4}=\frac{15}{4}$

Step2: Find a common denominator

The least common multiple of 3 and 4 is 12. $\frac{8}{3}=\frac{8\times4}{3\times4}=\frac{32}{12}$，$\frac{15}{4}=\frac{15\times3}{4\times3}=\frac{45}{12}$

Step3: Add the fractions

$\frac{32}{12}+\frac{45}{12}=\frac{32 + 45}{12}=\frac{77}{12}$

Step4: Convert back to a mixed number

$\frac{77}{12}=6\frac{5}{12}$

Answer:

$6\frac{5}{12}$