Draw the free body diagram:
Take the moment about Point A to reduce the amount of unknown forces.
$$$\sum M_A=0=Force \times Distance$$$
First, draw the free body diagram:
The triangular force distribution can be replaced with a concentrated force
, which is located through the triangle’s centroid. The force’s magnitude is equal to the triangle’s area:
is the triangle’s base, and
is the triangle’s height.
We can take the moment about Point A to reduce our unknown variables down to 1 (
will zero out since their radius vector goes through Point A). Remember,
$$Moment=Force \times Distance$$