In geometry, Heron's formula (sometimes called Hero's formula), named after Hero of Alexandria, gives the area of a triangle by requiring no arbitrary choice of side as base or vertex as origin, contrary to other formulas for the area of a triangle, such as half the base times the height. Use Heron's formula to find the area, in square yards, of ΔABC.

The area of ΔABC is 6√6 sq. yards.

Step-by-step explanation:

The area of a triangle using the Heron's formula is:

Here s is given as follows:

The sides of the triangle ABC are as follows:

AB = 6 yd

BC = 7 yd

CA = 5 yd

Compute the value of s as follows:

Compute the area of ΔABC as follows:

Thus, the area of ΔABC is 6√6 sq. yards.

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.