Guides that get things done.

Get a photo under 100 KB for an online form and keep it sharp: the two settings that matter, sizes for common limits, and why a file stays too big.

Sign a PDF on screen in a couple of minutes — in your browser, Adobe Reader, Preview or iPhone Markup — and know when a signature like this is legally enough.

Trailing commas, single quotes, “Unexpected token <”, NaN from Python: real JavaScript and Python error messages, what causes each and how to fix it.

Let guests join your Wi-Fi with one scan: how to make the code, why some scan but won't connect, and how to print one that works on every phone.

The percentage change formula with worked examples, plus percent vs percentage points, reversing a discount, negative values and multi-year growth.

$20 an hour is $41,600 a year at 40 hours a week. A full hourly-to-salary table from $15 to $50, plus the cases where the usual math is wrong.

What “£30,000 pro rata” really pays for part-time hours, how to work it out in seconds, and how part-time holiday entitlement is calculated.

The 28/36 rule lenders use to size your mortgage, with a worked example, how other debts shrink your budget, and how UK and Australian lenders differ.

A 15-year mortgage saves a fortune in interest; a 30-year one gives breathing room. The real numbers, and a third option most comparisons miss.

Why “rent is dead money” is only half true, a worked rent vs buy example with the break-even year, and the price-to-rent check that settles it fast.

How to calculate gross and net rental yield, the costs that turn 6% into 4%, and how to judge whether a buy-to-let's yield is actually good.