First reflection:
Focus in mirror `=-10cm`
`u=-15cm`
Applying mirror formula:
`(1)/(v)+(1)/(u)=(1)/(f)`
`v=-30cm`
For second reflectin on plane mirror:
`u=-10cm rArr v=10cm `
For third reflection on curved mirror again:
`u=-50 cm ` and `f=-10cm `
Applying mirror formula:
`(1)/(v)+(1)/(u)=(1)/(f)`
`rArr v=-12.5 cm`