Question

What is the sum of all integers that satisfy -3n<7n-20<3n

Answer 1

first let's solve the inequality

-3n<7n-20<3n
0<10n-20<6n
0<10n-6n<20
0<4n<20
0<n<5

n ∈ ]0,5[

the integers in this interval are 1,2,3,4 . their sum is 10