This is a correlation between MPG and Engine Size

cor.test(mtcars$mpg , mtcars$disp)
## 
##  Pearson's product-moment correlation
## 
## data:  mtcars$mpg and mtcars$disp
## t = -8.7472, df = 30, p-value = 9.38e-10
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
##  -0.9233594 -0.7081376
## sample estimates:
##        cor 
## -0.8475514

The p-value is 0.0000000000938 < alpha (0.05). Therefore there is a significant relationship.
The correlation is strong and negative. As the engine size is bigger, the MPG is lower.