To find 'd' choose one calculation:

Step-by-step explanation:

Since the whole base of the triangle is 14, we can half it to find the base of one triangle which is 7.

Pythagoras Theorem states a² + b² = c²

In this case a² = 7 and b² = 5 so,

a² + b² = c²

a² = 7 and b² = 5

7² + 5² = c²

49 + 25 = c²

74 = c²

√74 = c

go on the tube you might find some information there

2nd one in the first row is correct