Answer:
81 pounds.
Step-by-step explanation:
Let p represent Peter's weight, in pounds
Let s represent Susan's weight, in pounds
p = s + 12
p + s = 150
Now you can substitute the first equation into the second one.
s + 12 + s = 150
2s + 12 = 150
2s = 138
2s/2 = 138/2
s = 69
Since we know Peter's weight is 12 pounds heavier than Susan, and now that we also know Susan's weight, we can just add 12 pounds to Susan's weight or we can just plug it into the first equation.
p = 69 + 12
p = 81
