Exercice 24 ! Merci d'avance à ceux qui m'aideront !! :(

Exercice 24:

a)
A= (B*H) /2
A= (DM*DA) /2
A= 10x /2
A= 5x

b)
A₂ = ( (MC + AB) * BC) /2
A₂ = ( (15-x + 15) * 10) /2
A₂ = (  10(30-x) ) /2
A₂ = (300 -10x) /2
A₂ = 150 -5x

c)
A = 1/2 A₂
5x = 1/2 (150 -5x)
5x = 75 -5/2 x
10/2 x +5/2 x = 75
15/2 x = 75
x = 75 * 2/15
x= 10