Question

求出下列式子的过程（及答案）：0.4a+(84-a)*0.4*0.7=30.72

Answer 1

0.4a+(84-a)*0.4*0.7=30.72

0.4a+(84-a)*0.28=30.72

0.4a+23.52-0.28a=30.72

23.52+0.12a=30.72

0.12a=7.2

a=60