Answer: do your values into the equation A=1/2bh and do the math. First multiply the base (b) by 1/2, then divide the area (A) by the product. The resulting value will be the height of your triangle!
Total percentage allocated to food and housing is 19 + 21.5 = 40.5%
Annual income = $24000
Therefore: On food and housing, he plans to spend 40.5% of 24000
= 0.405 * 24000
= $9720