7. (5 points) There are several stamps with denominations of 0.5 yuan, 0.8 yuan, and 1.2 yuan, with a total denomination of 60 yuan. The number of 0.8 yuan stamps is 4 times the number of 0.5 yuan stamps. Therefore, the number of 1.2 yuan stamps is $\qquad$.

【Solution】Solution: Let the number of stamps with a face value of 0.5 yuan be $x$, then the number of stamps with a face value of 0.8 yuan is $4 x$, and let the number of stamps with a face value of 1.2 yuan be $y$. According to the problem, we can get the equation:
$0.5 x+0.8 \times 4 x+1.2 y=60$,
$3.7 x+1.2 y=60$,

Multiplying both sides of the equation by 10 gives: $37 x+12 y=600$,
which can be transformed into $y=\frac{600-37 x}{12}$,
Since $x$ and $y$ are integers, 600 is a multiple of 12, to make $600-37 x$ divisible by 12, $37 x$ must be a multiple of 12,

Since 37 is a prime number, the value of $x$ can only be a multiple of 12 to ensure that $y$ is an integer, thus we get:
When $x=12$, $y=13$;
Answer: There are 13 stamps with a face value of 1.2 yuan.
Therefore, the answer is: 13.