The sum of twice a and 4

Sorry if this isnt much info. That's all what was written in the paper

The way you wrote it could have 2 meanings:

Sum of twice a and 4 could be:

2a+4 or 2 (a+4) which will give different results.

In the first case:

2a+4

a = 4/2

a = 2

So the sum would be 2*2+4 = 4+4 = 8

In the second case:

2 (a+4) = 2a + 2*4 = 2a + 8

a = 8/2

a=4

2 (4+4) = 2*8 = 16