[mathsmanretired9848]

The E on M regression line passes through both means so it must beE - 50 = s(M - 45)where s is the the slope.If it predicts 70 as the English mark for mathematics 40 then70 - 50 = s(40 - 45)20 = -5ss = -4which is a weird result !Therefore the regression line isE - 50 = -4(M - 45)E - 50 = -4M + 180E = -4M + 230 or E = 230 - 4MIf M < 32.5 then E > 230 - 4*32.5 = 100 ----> E > 100If M > 57.5 then E < 230 - 4*57.5 = 0 ----> E < 0You may wonder why I have used the opposite sign in each of the last two lines. This is because multiplying by a negative number reverses the sign of an inequality.