When different types meet: type coercion

Look at the piece of code below. Select the lines that are written incorrectly:

val seven = 7.0
val five = 5

val toShort = seven.toShort()            // line 4
val sum = seven + five                   // line 5
val difference = seven - five.toDouble() // line 6
val toByte = seven.toByte()              // line 7
val mul = seven * five                   // line 8