3cubed-5[6-2 (9-2)squared]

So you want

pemdas

do 9-2 firtst
9-2=7

now we have


exponents
=3 times 3 times 3=27
=49

now we have
27-5(6-2(49))
do iner parenthasees multiplication
2(49)=98

now we have

27-5(6-98)
inner parenthasees

27-5(-92)
distribute (a(b+c)=ab+ac)
27-(-460)
27+460=487