Joanna bought 7 notebooks and 14 pencils
Step-by-step explanation:
Step 1 :
Let x denote the number of notebooks and y denote the number of pencils Joanna bought. 
Cost of one notebook = $ 2.30
Cost of one pencil = $1.42
Step 2 :
Total of notebooks and pencils bought  = 21
=> x + y = 21 => y = 21-x
Total cost of notebooks and pencils = $35.98
=> 2.3x + 1.42y = 35.98
Substituting y = 21- x here , we have,
2.3x + 1.42 ( 21-x) = 35.98
2.3x + 29.82 - 1.42x = 35.98
0.88 x = 6.16
=> x = 7
y = 21-x = 21-7 = 14
Step 3 :
Answer :
Joanna bought 7 notebooks and 14 pencils
 
        
             
        
        
        
Answer:
In quadrilateral ABCD we have
 AC = AD
 and AB being the bisector of ∠A.
 Now, in ΔABC and ΔABD,
 AC = AD
[Given]
 AB = AB
[Common]
∠CAB = ∠DAB [∴ AB bisects ∠CAD]
 ∴ Using SAS criteria, we have
 ΔABC ≌ ΔABD.
 ∴ Corresponding parts of congruent triangles (c.p.c.t) are equal.
 ∴ BC = BD.
 
        
             
        
        
        
Answer:
1 and 1/2
Step-by-step explanation:
3 1/4 is equal to 13/4 and 1 3/4 is equal to 7/4. 13/4 - 7/4 is 6/4. 6/4 equalsn is 1 1/2.
 
        
             
        
        
        
Answer: 82
Step-by-step explanation:
59+23=82
Check
82-23=59