Help please, im dum-

65 8 7 4 5 6 8 4 3 2 1 9 5 6 4 2 1 6 5 1 5 1 3 2 3 5 multiply the third number in the first row by the seventh number in the third row. add this result to the fifth number in the second row. add to this total ten times the fourth number in the third row. subtract the eighth number in the first row from the result.

What is the difference between regular convex and concave polygons

In triangle △abc, ∠abc=90°, bh is an altitude. find the missing lengths. ah=4 and hc=1, find bh.