The graph shows the possible combinations of the number of pounds of tangerines and lemons that could be purchased for...

1. TRANSLATE the problem information

The problem tells us:

• The graph shows combinations of tangerines (x-axis) and lemons (y-axis) that cost $18
• Melvin bought 4 pounds of tangerines
• We need to find how many pounds of lemons he bought

What this means mathematically:

• We're looking for the point on the line where \(\mathrm{x = 4}\)
• The y-coordinate of that point is our answer

2. VISUALIZE by locating the point on the graph

To read a graph for a specific x-value:

• Find \(\mathrm{x = 4}\) on the horizontal axis (pounds of tangerines)
• Move straight up from \(\mathrm{x = 4}\) until you hit the line
• From that intersection point, move horizontally to the y-axis
• Read the y-value

3. Read the y-coordinate

When \(\mathrm{x = 4}\), the line passes through \(\mathrm{y = 10}\).

This means: If Melvin bought 4 pounds of tangerines, he bought 10 pounds of lemons.

Answer: B. 10

Why Students Usually Falter on This Problem

Most Common Error Path:

Weak VISUALIZE skill: Students misread which axis represents which quantity

Some students see "4 pounds of tangerines" and look at the y-axis instead of the x-axis, or they confuse what they're solving for. They might:

• Think they need to find x when \(\mathrm{y = 4}\)
• Look at where \(\mathrm{y = 4}\) and read \(\mathrm{x = 14}\) from the graph

This may lead them to select Choice C (14)

Second Most Common Error:

Weak VISUALIZE skill: Students misread the grid lines on the graph

The graph has gridlines at every unit, and students might:

• Count incorrectly from the origin
• Misalign their reading of where \(\mathrm{x = 4}\) intersects the line
• Read \(\mathrm{y = 7}\) instead of \(\mathrm{y = 10}\)

This may lead them to select Choice A (7)

The Bottom Line:

This problem tests careful graph reading more than complex mathematics. The key is accurately matching the verbal description ("4 pounds of tangerines") to the correct axis (x-axis), then precisely reading the corresponding value on the other axis. Students who rush or don't carefully track which variable goes with which axis often make simple but costly errors.