Error: 'int' object is not subscriptable - Python

The problem is in the line,

int([x[age1]])

What you want is

x = int(age1)

You also need to convert the int to a string for the output...

print "Hi, " + name1+ " you will be 21 in: " + str(twentyone) + " years."

The complete script looks like,

name1 = raw_input("What's your name? ")
age1 = raw_input ("how old are you? ")
x = 0
x = int(age1)
twentyone = 21 - x
print "Hi, " + name1+ " you will be 21 in: " + str(twentyone) + " years."

When you type x = 0 that is creating a new int variable (name) and assigning a zero to it.

When you type x[age1] that is trying to access the age1'th entry, as if x were an array.