we get

a- 0.75a=210

ie 0.25a=210

ie a=210*4

ie a=840

a = 210 + 0.75a

Solving

a = 210 + 0.75a

Solving for variable ‘a’.

Move all terms containing a to the left, all other terms to the right.

Add ‘-0.75a’ to each side of the equation.

a + -0.75a = 210 + 0.75a + -0.75a

Combine like terms: a + -0.75a = 0.25a

0.25a = 210 + 0.75a + -0.75a

Combine like terms: 0.75a + -0.75a = 0.00

0.25a = 210 + 0.00

0.25a = 210

Divide each side by ‘0.25’.

a = 840

Simplifying

a = 840

a-0.75a=210

aX(1-0.75)=210

a X 0.25=210

a=210:0.25

a=840

Sorry i am not learning english so i dont know what kind math language all of u r using , but i think my reply is correct . Hope u understand

.25a=210

divide by .25