Solve the proportion and ch \[ \frac{a}{10}=\frac{a+6}{7} \]

Step 1 ：Let's solve the proportion \(\frac{a}{10} = \frac{a+6}{7}\).

Step 2 ：We can solve it by cross-multiplication, which means we multiply the numerator of the first fraction by the denominator of the second fraction and set it equal to the numerator of the second fraction multiplied by the denominator of the first fraction.

Step 3 ：This will give us an equation in terms of 'a' which we can solve.

Step 4 ：By solving the equation, we find that the solution is -20.

Step 5 ：Final Answer: The solution to the proportion is \(\boxed{-20}\).