Can someone help me with the appropriate equation for the following question?

What is the IRR of the following cashflows?

Now: - $120

After 1 year: + $20

After 2 years: + $90

After 3 years: - $10

After 4 years: + $30

After 5 years: + $30

After 6 years: + $30

After 7 years: + $40