I.e., 1. Get the difference between MHR and RHR. 2. Multiple by intensity 3. add RHR.
If the formula in the article were followed, the steps for calculating target heart rate would be: 1. get the difference between MHR and RHR. 2. get the sum of intensity and RHR. 3. multiply the difference (from step 1) and the sum (from step 2).