What is the area step by step to understand and what is perimeter step by step and the type i don't know

Area is you multiply 7.9 by 5.9 then divide by two and then the perimeter is you add 7.9+5.9+9.86 I think

To find the area of a triangle, use the formula a=(1/2)bh.
a = area
b = base
h = height
So using the measurements in the picture...
b = 7.9
h = 5.9
Now using the measurement ^ to fill in the formula.
a=(1/2) 7.9 * 5.9
Now multiply the numbers to find a.
a=(1/2) 7.9 * 5.9
a= 3.95 * 5.9
a = 23.305
The area is 23.305 mm.

To find the perimeter, add up all the sides.
7.9 + 5.9 + 9.86
13.8 + 9.86
23.66
The perimeter is 23.66 mm.

The type of triangle is a right triangle because one of the angles is a right angle (90 degrees).