Question

Let's say I am given a table of information for the values of the real GDP, consumption, investment, exports, and imports. There was an equilibrium GDP where the real GDP = Aggregate Expenditure = C + I + X - IM. If the value of investments changed (went from 100 to 160), I had to calculate the new equilibrium GDP. But I did so by trial and error and was wondering if there was an easier/quicker way to do it. I have the multiplier values for consumption and imports.