unsupported operand type(s) for %: 'list' and 'int'

[stullis]

Because "a" is a list, you cannot simply perform mathematics with it. You can iterate over "a" and take the modulus of each number in it:

a = []
k=1

for x in range(0,10):
    a.append(int(input()))
    
for x in a:
    if (x % 2 == 0):
        k *= x

print(k)