Need help wit this problem X/fx

2 3/4
-1 3/2
0 3
1 6
2 12

tht's the table, wish I can take a pic of 2

Grandpa ernie is shrinking! over the past 4 years his height decreased by a total of 2.4 cm.it decreased by the same amount each year. what was the change in grandpa ernie's height each year