Proof by Substitution

---

(left (make-pair 10 20))
(left (lambda (which?)
        (if (= which? 1) <10> <20>)))
((lambda (which?) (if (= which? 1) <10> <20>)) 1)
(if (= <1> <1>) <10> <20>)
(if <#T> <10> <20>)
<10>


Jim Miller