Carbon-12 can be pictured as three helium-4 nuclei bound together, and oxygen-16 as four…

Step 1. Carbon-12. $3 \times 4.002603\ \text{u} - 12.000000\ \text{u} = 0.007809$ u. So $E = 0.007809\ \text{u} \times 931.494\ \text{MeV/u} = 7.274$ MeV, which rounds to $7.27$ MeV.

Step 2. Oxygen-16. $4 \times 4.002603\ \text{u} - 15.994915\ \text{u} = 0.015497$ u. So $E = 0.015497\ \text{u} \times 931.494\ \text{MeV/u} = 14.44$ MeV.

Why not the full binding energy? The binding energy of carbon-12 is $92.16$ MeV, to pull it into $12$ separate nucleons. Here the pieces are helium-4 nuclei, which keep their own $28.30$ MeV each. We pay only the difference: $92.16\ \text{MeV} - 3 \times 28.30\ \text{MeV} = 7.27$ MeV.