Mental math is something that can be done i your head.
for example you can do 1+1 in your head and you dont need a calculator or paper to do it so i would be called mental math
Hope this helps
remember if you ever need anything and you dont want to waste points you can just post it on my pfp or message me the question
well first the complement I 90-19=71
and supplement is 180-19=161
Question-
6/15 divided by 1/7
Answer-
Find the reciprocal of the divisor
Reciprocal of 1/7: 7/1Now, multiply it with the dividend
So, 6/15 ÷ 1/7 = 6/15 × 7/1= (6 × 7)/(15 × 1) = 42/15After reducing the fraction, the answer is 14/5In mixed form: 2 4/5
Only one that would make sense is 1/12
28, by the way you could’ve just used a calculator