Contribution by each factor
The easiest consistent explanation is using multiplication: The Q2 estimated loss of $231$ is $\frac{231}{150}=1.54$ times the Q1 estimated loss of $150$.  This is a combination of


The exposure being $1.5$ times the previous figure 
The loss given default being about $0.933$ times the previous figure 
The probability of default being $1.1$ times the previous figure 


and this is consistent with $1.5\times 0.933 \times 1.1 \approx 1.54$ - it does not matter which order you do the multiplication

It is not that far away from saying $50\% -6.7\% + 10\%$ is about $54\%$, except that that is not precise (they actually add up to $53.3\%$ and other examples could be worse) but this would be talking about percentage changes in percentages, which is often confusing

If you looked at the effect on the old estimated loss of $150$ of each change if the others had not changed, you would have got $+75$ (not $+76$), $-10$, $+15$ which add up to $+80$ rather than the actual $+81$, and other examples could be worse