Print numbers from 1-50

A shell is not a (good) programming language, it's (before all) a command line interpreter. Use a counting command if you want to count, not the echo and [ commands in a loop.

For instance, GNU systems have the seq command for that. Alternatives are awk or bc for instance:

seq 50
echo 'for (i=1; i<=50; i++) i' | bc
awk 'BEGIN {for (i=1; i<= 50; i++) print i}'

If you find yourself using a loop in shells, chances are you're going for the wrong approach.

On line 5: Change $x=(($x + 1)) to x=$(($x + 1)).

Instead of using an entire bash script, you can just use seq 1 50.

If the case were x=$(($x + 2)), you could use seq 1 2 50, where 2 denotes step/increment.

Print numbers from 1-50

printf '%s\n' {1..50}

print numbers from 1-50 with step say 2 (bash 4+):

printf '%s\n' {1..50..2}