influence of growing foreign demand for local products on the net exports in a fixed exchange rate regime Suppose we have a country $A$ with a fixed exchange rate regime.

Suppose that, suddenly, the foreign demand for $A$'s made products rose up.

What will happen to $X-IM$?

As far as I can tell $X$ grows and thus $GNP$ grows. Finally since $GNP$ grows and the exchange rate is fixed $IM$ grows. So, finally we can't say anything about $X-IM$?
Yes, $IM$ increases in the equilibrium, but, no, $IM$ cannot increase more than $X$ does.

Logical explanation: "$\Delta X &lt; \Delta IM$ in the equilibrium" means that $A$'s GNP decreases. When GNP decreases, we have $\Delta IM &lt; 0$ while $0 &lt; \Delta X$ so we can't have $\Delta X&lt;\Delta IM$. Contradiction! We can never have $X-IM$ decreasing in the equilibrium.

Mathematical illustration: Consider the model $Y=C+I+G+X-IM$, $C=a+bY$, $IM=c+dY$. Then the equilibrium is $Y = (a-c+I+G+X)/(1-b+d)$. When $X$ increases by $\Delta X$, $\Delta Y = \Delta X / (1-b+d)$ and $\Delta IM = d\Delta X / (1-b+d)$. Thus,
$$\Delta X - \Delta IM = \left(1 - \frac{d}{1-b+d} \right) \Delta X = \left( \frac{1-b}{1-b+d} \right) \Delta X &gt; 0.$$