Question

2/5r -5 =7 ( what's r )

Answer 1

2/5r-5=7
2/5r-5+5=7+5
2/5r=12
2/5r*5r=12*5r
2=60r
2/60=60r/60
1/30=r
which is 0.0333333333333 = r
I'm pretty sure this is correct because I double checked it

Answer 2

$\frac{2}{5} r-5=7\\\\ \frac{2}{5}r=12\\r=12\times \frac{5}{2} \\r= 6 \times 5\\ r=30$