Phyiscs 1

On a spacecraft, two engines are turned on for 750 s at a moment when the velocity of the craft has x and y components of v0x = 4280 m/s and v0y = 5495 m/s. While the engines are firing, the craft undergoes a displacement that has components of x = 4.60 106 m and y = 6.12 106 m. Find the x and y components of the craft's acceleration.

So I got the right answers, but I am not sure how to do it.

Wouldn't taking the X & Y displacement and putting that over time give you the new velocity --> and we know change in velocity over time is acceleration. However, I did this and had to multiply THAT answer by 2 to get the right answer? Please explain!