2{[5(c-4)+15]-[3(5c-3)+1]}

Can someone help me to figure out this equation. I don't remember how to do this with the outside brackets

start with the innermost brackets and work outwards

2{[5(c-4)+15]-[3(5c-3)+1]}
= 2{[5c-20+15]-[15c-9+1]}
= 2{[5c-5]-[15c-8]}
= 2{5c-5-15c+8]}
= 2{-10c+3]}
= -20c + 6