Question

two sides of a circular field 85 and 154 metre in the length and its perimeter is 324 find the area of field

Answer 1

Since, in comments you said that it is not circular field but triangular
Then,
Side1 = 85m Side2 = 154m Side3 =?
Let Side 3 be x ( just for simplified answer otherwise no need of supposing)

Perimeter = 324m²

Perimeter of triangle = Sum of the three sides
$324 = 154 + 85 + x \\ 324 = 239 + x \\ x = 324 - 239 \\ x = 85$
Therefore, the third side of the triangle is 85 m

Hope, it helps