we can solve this by expresing their work in rate as how fast they are doing.
Max mows at speed of 1/45
Jan takes 1/90
When we sum those 2 rates we calculate how much will need for them to mow the lawn or in other words their sum to equal 1
1/45x + 1/90 x= 1
3/90x = 1
1/30x = 1
x = 30
Answer is 30