○=△+△+△+△ ○+△=30

Four δ+δ+δ+δ plus 1δ= 5δ= 30δ= 30÷5 = 6.

○=△+△+△+△ =6*4=24

△+△+○= 16 △+○= 14 Replace △+○= 14 in the formula, that is, △+ 14= 16.

△=2 ○= 14-2= 12

Definition of equivalent substitution:

Substitute one quantity (or part of a quantity) for another quantity (or part of another quantity) equal to it. "Equivalent substitution" means that a quantity is replaced by an equivalent quantity, which is a basic thinking method in mathematics and the basis of algebraic thinking method. The narrow sense of equivalent substitution is embodied in the nature of equality, that is, the transitivity of equality: if a=b and b=c, then a = C.