Answer :
We are given an isosceles triangle with two congruent sides of length $x$, and the shortest side with length $y$. The perimeter of the triangle is the sum of all its sides. Therefore, the perimeter $P$ is given by:
$$
P = y + 2x
$$
We know that the perimeter is $7.5$ m and that the shortest side measures $y = 2.1$ m. Substituting the value of $y$ into the equation gives:
$$
2.1 + 2x = 7.5
$$
Thus, the equation that can be used to find the value of $x$ is:
$$
2.1 + 2x = 7.5
$$
This corresponds to the fourth option.
$$
P = y + 2x
$$
We know that the perimeter is $7.5$ m and that the shortest side measures $y = 2.1$ m. Substituting the value of $y$ into the equation gives:
$$
2.1 + 2x = 7.5
$$
Thus, the equation that can be used to find the value of $x$ is:
$$
2.1 + 2x = 7.5
$$
This corresponds to the fourth option.
