Successive percentage change

% increase is 120% * 110% - 100% = 32%

Let the initial salary of Ram be ₹1.

Salary of Ram after increment = $$₹\left(1+10\%\right)\left(1+12\%\right)\left(1+15\%\right)=₹1.4168$$. 

So, the salary of Ram increased by 41.68%.

Average yearly increment in his salary = $$\dfrac{41.68\%}{3}=13.89\%$$

If all sides are increased proportionately and the perimeter increased by 10%, then all the sides increase by 10%.
So, the height of the triangle also increases by 10% and the area increases by 110%*110% - 100% = 21%