For B tree
Order 12 means 11 nodes in 1st level and 12 nodes are in rest levels
So for 1st level 11 nodes
2nd level 12*11=132 nodes
3rd level 132* 12=1584 nodes
4th level 1584*12=19008 nodes
So, 4 levels are required for 7000 nodes
B+ tree
Same for B+ tree
But it should count from leaf level
So, for 1st level ceil(7000/12)=583 nodes
2nd level ceil(583/12)=49 nodes
3rd level ceil(49/12)=4 nodes
4 th level ceil(4/12)=1 node
So, here also 4 levels required for accomodate all 7000 nodes
So, difference between levels of b tree - b+tree = 4-4=0