Update src/7_tight_binding_model_sol.md

src/7_tight_binding_model_sol.md

@@ -103,7 +103,7 @@ pyplot.tight_layout();
 
 ### Subquestion 4
 
-Plots for 2t'=t, 4t'=t and 10t'=t.
+Plots for 2t'=t, 4t'=t and 10t'=t:
 
 ```python
 k1 = np.linspace(-pi, -pi/2-0.01, 300);