879,087.
Step-by-step explanation
To find the number of lawnmowers, we need to first find 70% of the number of lawnmowers that was kept in the past. Then add the to the number of lawnmowers kept in the past.
From the given question;
Number of lawnmowers kept in the past = 517, 110.
70% of lawnmowers kept in the past = 70% of 517 110

Number of lawnmowers now kept in store = number of lawnmowers kept in the past + 70% of lawnmowers kept in the past
= 517 110 + 361 977
= 879,087.