The equation is

₃Li⁷ + ₁H¹ —–→ ₄Be⁷ + ₀n¹ + E

Now mass of ₃Li⁷ = 7.01823 u

Mass of ₁H¹ = 1.00814 u

Mass on LHS = 7.01823 + 1.00814 = 8.02637 u

Mass of ₄Be⁷ = 7.01592 u

Mass of ₀n¹ = 1.00866 u

Mass on RHS = 8.02458 u

Difference in masses, Δ m = 0.00179 u

When converted to energy, this will be the K.E of the proton.

0.00179 u = 931.5 × 0.00179 = 1.667 MeV.