Hey there!!
Remember PEDMAS ?
P = parenthesis
E = exponents
D = division
M = multiplication
A = addition
S = subtraction
THE ORDER OF BRACKETS -
( ) - solved first
[ } - solved second
{ } - solved third
Now, according to PEDMAS , we will need to solve the brackets first
3j - { 2k - [ 5h - ( 3j + k )]}
3j - { 2k - [ 5h - 3j - k ]}
3j - { 2k - 5h + 3j + k ]
3j - { 3k - 5h + 3j }
3j - 3k + 5h - 3j
5h - 3k is the final answer
Hope my answer helps!