If triangles/parallelograms have the same height, their area ratio equals their base ratio.
#1 If two shapes are congruent (that means you can shift, rotate and/or reflect so
that they coincide), then their areas are equal.
#2 If triangles/parallelograms have the same height, their areas’ ratio equals their
#3 Sometimes, two shapes can have the same area even if they are not congruent.
Drawing a construction line splits the diagram into various parallelograms and triangles with the same height, for which we can compare the ratios. Using congruent triangles, we realise that two of the smaller parallelograms have the same area even though they are not congruent. With the right perspective, we can deal with these perplexing parallelograms. Using comparison, we found the area of the small triangular piece x, and from there we use fact #2 above to work out the rest.