How to calculate the problem that 3 of 4 [x + 5] plus 10 [x + 3] equals 4

How to calculate the problem that 3 of 4 [x + 5] plus 10 [x + 3] equals 4

3(x+5)/4-7(x+3)/10=4
Multiply both sides of the equation by 20, and the equation still holds
3*(x+5)*5-7*(x+3)*2=80
15x+75-14x-42=80
x+33=80
x=47

X to 10 / 7 is 0.4x plus 12

x/(10/7)=0.4x+12
7/10x=4/10x+12
7/10x-4/10x=12
3/10=12
x=12*10/3
x=40

It is proved that (x-1) (x-3) (X-5) (X-7) + 16 is a complete square expression

Solution (x-1) (x-3) (X-5) (X-7) + 16
=(x-1)(x-7)(x-3)(x-5)+16
=(x^2-8x+7)（x^2-8x+15）+16
=[(x^2-8x)+7][（x^2-8x）+15]+16
=(x^2-8x）^2+22(x^2-8x)+105+16
=(x^2-8x）^2+22(x^2-8x)+121
=(x^2-8x）^2+2×11(x^2-8x)+11^2
=(x^2-8x+11)^2
so
(x-1) (x-3) (X-5) (X-7) + 16 is a complete square