Take the ingredients of batch A and list them. This equals 3 cups. Take the ingredients of batch B and multiple them by 1.2 then list them. This makes 1 1/2 cups. Add the amounts listed in A to the amounts listed in B and add them together. The result will be 4 1/2 cups of your new batch C.
Jim - Another transplanted Texan
Former KCBS CBJ
Large and Medium Big Green Eggs , Black 18.5" WSM, Blue Weber Performer - Stainless, Green Weber OTG Kettle , Brinkmann SnP Pro, and a Stainless UDS. One retired Portable Kitchen grill.
Red Thermapen, Maverick ET-732, EdgePro Apex Sharpener.
Avatar is the original 1951 Weber Kettle