yes because there is an invisible one in fron to y
1y means 1 times y
basically you can multiply 1 times anything and it will remain the same so therefor
y=1y=(1)(y)=(1)(1)(y)=(1)(1)(1)(y)=(1)(1)(1)(1)(1)(1)(1)(1)(1)(1)(1)(y) etc
so basically he is correct since y=1y so therefor
y+4=1y+4
subtract 4 from both sides
y=1y
subsitute
y=1y
1y=1y
true
