To begin you must subtract the cost of the roses from the total cost of the flowers sold so $73-$28. Then divide the remainder by the number of decorated flowers she sold to get the cost per each decorated flower. I do not see in your question the number of decorated flowers she sold. I see "a" so perhaps she sold one???
Because the side has to be increased by 50% you find half of 8, which is 4 and you add 8+4 because you add the increased amount 8+4=12 you then just find the area.... so 12x12= 144
