Graphic algebra problems. Very hard

Select your preferred difficulty level for algebra exercises. Very hard. Free and interactive.

15 + 1 - shell.png = sun 1.png - 2
18 + 1 - hibiscus.png = shell.png + 1
sun 1.png + 1 = 16 + 3 - hibiscus.png
Can you calculate the value of each of the elements?
hibiscus.png =
shell.png =
sun 1.png =