35% is 35/100 or 0.35
of is multiply so
34% of x = 12780 becomes
0.35 * x = 12780 now divide both sides by 0.35 so that the 0.35 on the left cancels out
x = 12780/0.35
$${\frac{{\mathtt{12\,780}}}{{\mathtt{0.35}}}} = {\mathtt{36\,514.285\: \!714\: \!285\: \!714\: \!285\: \!7}}$$
$36514.29
35% is 35/100 or 0.35
of is multiply so
34% of x = 12780 becomes
0.35 * x = 12780 now divide both sides by 0.35 so that the 0.35 on the left cancels out
x = 12780/0.35
$${\frac{{\mathtt{12\,780}}}{{\mathtt{0.35}}}} = {\mathtt{36\,514.285\: \!714\: \!285\: \!714\: \!285\: \!7}}$$
$36514.29