         NSLayoutConstraint.width(
             view:buttonBack,
             constant:kBackWidth)
+        
+        NSLayoutConstraint.height(
+            view:collectionView,
+            constant:kCellSize)
+        NSLayoutConstraint.bottomToBottom(
+            view:collectionView,
+            toView:self)
+        NSLayoutConstraint.equalsHorizontal(
+            view:collectionView,
+            toView:self)
     }
     
     required init?(coder:NSCoder)

import UIKit

class VLinearEquationsSolutionBar:UIView
{
    private let model:MLinearEquationsSolutionBar
    private weak var controller:CLinearEquationsSolution!
    private let kBorderHeight:CGFloat = 1
    private let kBackTop:CGFloat = 20
    private let kBackWidth:CGFloat = 60
    private let kBackHeight:CGFloat = 44
    
    init(controller:CLinearEquationsSolution)
    {

            action:#selector(actionBack(sender:)),
            for:UIControlEvents.touchUpInside)
        
        let collectionView:VCollection = VCollection()
        collectionView.isScrollEnabled = false
        collectionView.bounces = false
        collectionView.delegate = self
        collectionView.dataSource = self
        self.collectionView = collectionView
        
        if let flow:UICollectionViewFlowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout
        {
            flow.scrollDirection = UICollectionViewScrollDirection.horizontal
            flow.itemSize = CGSize(width:kCellSize, height:kCellSize)
            flow.sectionInset = UIEdgeInsets(
                top:0,
                left:kBackWidth,
                bottom:0,
                right:0)
        }
        
        addSubview(border)
        addSubview(collectionView)
        addSubview(buttonBack)
        
        NSLayoutConstraint.bottomToBottom(
