Answer:
Dad made 90 steps during that period.
Step-by-step explanation:
Let x,y,z be the steps made by dad,Anna and Todd.
Given that while dad made 3 steps, Anna made 5 steps.
That is
And for every 3 steps Anna made, Todd made 5 steps.
That is
It is also given that total number of steps made by Anna and Todd is 400.
That is y+z=400
let us plugin y and z in terms of x.
Hence Dad made 90 steps during that period.