This is a discrete frequency distribution of goals against number of matches, so the mean uses $\sum fx/\sum f$.

$\sum fx = 33$, $\sum f = 20$

$\bar{x} = \dfrac{33}{20} = 1.65$

Using $\bar{x} = \dfrac{\sum fx}{\sum f}$ for this discrete frequency distribution:

Step 1 — Tabulate $fx$.

Step 2 — Sum. $\sum f = 3+6+7+3+1=20$ (matches the stated 20 matches). $\sum fx = 0+6+14+9+4 = 33$.

Step 3 — Divide.

Independent check. Re-adding the $fx$ column as $(6+9)+(14+4)+0 = 15+18+0=33$ — confirms the total.

Averaging the five listed goal-values directly (getting 2) instead of weighting by how many matches had each goal count is the typical mistake. Also check that $\sum f$ matches the stated total number of matches (20) before dividing.