Answer 1

its not line 16 but line 14, where you dont close () and start with *:

print((*22/7*int(x)*int(x))+((22/7*int(x)*int(z)))

should be

print((22/7*int(x)*int(x))+((22/7*int(x)*int(z))))

as for the other question, you can check the value before using it, like if not none or something