Answer:
4
Step-by-step explanation:
Both triangles are the same shape, just to different scales. In order to find out the length of side AB in triangle ABC, you have to find out the length of side PQ in triangle PQR and how much bigger than side AB is.
You can tell that sides AC and PR are similar, and 30/5 is 6. You see also that sides BC and QR are similar, and 42/7 is also 6. We have now discovered that triangle PQR is 6 times bigger than triangle ABC.
So now, to find the length of the missing side, we have to shrink side PQ by 6. 24/6 is 4. Therefore, the length of side AB is 4.
