Question

(30 × 10 ) - 4 × a + 50 × 2 ) = 100

Answer 1

300-4xa+100=100
300-4xa=100-100
300-4xa=0
4xa=300+0
4xa=300
a=300:4
a=75

Answer 2

300-4a+100=100
4a+100=400/-100
4a=300
a=300:4
a=75