Total number of equal parts:
4+5= 9
Each part is:
45 cans/ 9 parts= 5 cans/part.
Group 1 has 4 parts, so group 1 has:
5 cans/part* 4 parts= 20 cans.
Group 2 has 5 parts, so group 2 has:
5 cans/ part* 5 parts= 25 cans.
Group 1 has 20 cans, group 2 has 25 cans~