so here it is in math form (plug into calculator
1.06 means add 6% of whatever you have
so
55*1.06+20= first year
so what you do is just keep multiplying this quantity by 1.06 then adding 20 then multiplying, etc
the long form would be
[([([([([55*1.06+20]*1.06+20)*1.06+20]*1.06+20)*1.06+20]*1.06+20)*1.06+20]*1.06+20)*1.06+20]*1.06+20=362.1125
round
$362.11 after 10 years