sicp-ex-1.3

Here's a version with simpler logic to detect the smallest of the three values:

 (define (ssq a b) (+ (* a a) (* b b))) 
  
 (define (sumOfLargestTwoSquared x y z) 
   (cond ((and (<= x y) (<= x z)) (ssq y z)) 
         ((and (<= y x) (<= y z)) (ssq x z)) 
         (else (ssq x y)))) 

Another possibility (uses some language constructs that haven't been introduced yet):

  
 (define (square x) 
   (* x x)) 
  
 (define (sum-of-squares x y) 
   (+ (square x) (square y))) 
  
 (define (sum-of-squares-of-two-largest x y z) 
   (let* ((smallest (min x y z)) 
          (two-largest (remove smallest (list x y z)))) 
     (apply sum-of-squares two-largest))) 

  
 (define (square x) 
   (* x x)) 
  
 (define (sum-of-squares x y) 
   (+ (square x) (square y))) 
  
 (define (sum-of-squares-of-two-largest x y z) 
   (sum-of-squares (max x y) (max (min x y) z)))