For the first triangle, we have,
Base = 15 cm and altitude = 7 cm
Thus, area of a triangle =
=
It is given that the area of the first triangle and the second triangle are equal.
Area of the second triangle = 52.5 cm2
One side of the second triangle = 10.5 cm
Therefore,
The other side of the second triangle =
=
Hence, the other side of the second triangle will be 10 cm.