my route do not work ,use express and ejs

i want to click link to solution page,but my route don't work,what's wrong?

1. app.js

   var express = require('express'); var path = require('path'); var
   favicon = require('serve-favicon'); var logger=require('morgan');
   var cookieParser = require('cookie-parser'); var bodyParser =
   require('body-parser'); var expressLayouts =
   require('express-ejs-layouts');
   
   var index = require('./routes/index'); var users =
   require('./routes/users');
   
   var app = express();
   
   app.set('layout', 'layout/layout'); app.set('view engine', 'ejs');
   
   app.use(expressLayouts);
   app.use(logger('dev')); app.use(bodyParser.json());
   app.use(bodyParser.urlencoded({ extended: false }));
   app.use(cookieParser()); app.use(express.static(path.joindirname,
   'public')));
   
   app.use('/', index); app.use('/users', users); app.use('/solution',
   index);
   
   

   2.routes/index var express = require('express'); var router = express.Router();

   router.get('/', function(req, res) {
        res.render('pages/index'});
   });
   
   router.get('/solution', function(req, res) {
        res.render('pages/solution');
   });
   
   module.exports = router;