JSFiddle - React, Tailwind, and code Playground

JavaScript

function checkResult (A, K, B, M, X, d) {
  const d_A = d - Math.floor(d/K);
  const d_B = d - Math.floor(d/M);
  return ( (A*d_A + B*d_B) < X );
}

let A = 19;
let K = 3;
let B = 14;
let M = 6;
let X = 113;

let $otvet = 0;

let d = X*M*K/(A*M*(K-1) + B*K*(M-1));

d_MIN = Math.floor(d);
d_MAX = Math.ceil(d);

if (!checkResult(A, K, B, M, X, d_MIN)) {
   $otvet = d_MIN;
} else {
  $otvet = d_MAX;
};

console.log($otvet);