step by step would be: 7=b-12 in order to find out what b is you have to do the opposite of what's being added, subtracted, multiplied, or divided. In this case 12 is being subtracted from b (-12) so you add 12 (+12) to both sides of the equal sign so your equation now looks like this and is ready to be solved: 7+12=b(-12)+12 which = 19=b