JSFiddle - React, Tailwind, and code Playground
JavaScript
f=(a,b,c)=>a<=b?1:1+f(a-b+c,b,c)
console.log(f(30, 3, 2)); // -> 28
console.log(f(84, 17, 15)); // -> 35
console.log(f(79, 15, 9)); // -> 12
console.log(f(29, 17, 4)); // -> 2
console.log(f(13, 18, 8)); // -> 1
console.log(f( 5, 5, 10)); // -> 1
console.log(f( 7, 7, 7)); // -> 1
console.log(f(69, 3, 8)); // -> None
console.log(f(81, 14, 14)); // -> None